UNITED STATES DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY

40Ar/38Ar Age-Spectrum Data for Rocks of the Bronson Hill Terrane, Central New England

by

Julie L. Boyd1, Michael J. Kunk2, and Robert P. Wintsch3

Open-File Report 94-126 January 1994

This report is preliminary and has not been edited or reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature. Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S.G.S.

1 U.S. Geological Survey, MS 981, Reston, Virginia 22092, and Department of Geological Sciences, Indiana University, Bloomington, Indiana 47405

2 U.S. Geological Survey, MS 981, Reston, Virginia 22092

3 Department of Geological Sciences, Indiana University, Bloomington, Indiana 47405

FROK BEST WASLABLE CCflf TABLE OF CONTENTS

INTRODUCTION 3

SAMPLING STRATEGY 3

METHODS 5

Sample Preparation 5

Sample Analysis 5

Isotopic Data Reduction 6

SAMPLE DESCRIPTIONS 8

RESULTS 20

Condensed Tabular Argon Data 22

*Ar/*Ar Data 24

ACKNOWLEDGEMENTS 126

REFERENCES 126 INTRODUCTION

The purpose of this report is to present 40Ar/38Ar data from hornblende, biotite, and muscovite separated from metamorphic rocks collected from the Bronson Hill terrane in central New England (Fig. 1). This data was collected to characterize the metamorphic/cooling history of the Bronson Hill terrane. In the central part of the New England Appalachians the Bronson Hill terrane lies close to the Acadian metamorphic high (Robinson, et al., 1986), but to the south the effects of Alleghanian metamorphism become stronger Brookins, 1970; (Brookins and Armstrong, 1980; Pressel and Armstrong, 1980; Wintsch and Sutter, 1986). The scientific goal of this study is to characterize the transition between the northern Acadian and southern Alleghanian orogenic events in the Bronson Hill terrane. Ultimately, the comparison of the metamorphic cooling history of the Bronson Hill terrane with that of adjacent terranes will allow for a better understanding of the regional tectonothermal evolution of this portion of New England and may reveal some history of terrane assembly. The primary approach used in this research is 40Ar/38Ar mineral age dating (thermochronology). This method monitors the time-temperature history preserved in mineral isotopic compositions, and is especially useful in constraining the times of cooling through closure (Dodson, 1973) from peak metamorphic conditions. The results of our analysis are presented in this report; a preliminary geological interpretation of these results appear in Boyd, et al. (1993) and Wintsch, et al. (1993a;b).

SAMPLING STRATEGY

To characterize the transition between the metamorphic histories of Acadian and Alleghanian orogenic events in the Bronson Hill, samples were collected along a north-south traverse (Fig. 1). The northern limit of sampling was the southern Pelham dome which connects our data to that of Spear and Harrison (1989), and Tucker and Robsinson (1990; 1993) in northcentral Massachusetts and adjacent New Hampshire (Harrison et al. 1989). Samples were collected at 5-10 km intervals from the southern Pelham dome south to Long Island Sound. Amphibolites, granodioritic gneisses, muscovite schists, and pegmatites were collected, and hornblende, muscovite, and biotite were separated. Pelham Dome

Massachusetts I / Connecticut i_

LEGEND Willimantic O This Study ° Tucker & Robinson 1990 Glaston Window $ Spear & Harrison 1989 Dome + Harrison et. al, .1989 A Brookins & Armstrong 1980 v Brookins 1970 Wintsch & Sutter 1986 X Pressel & Armstrong 1980

1-95 New Haven *

Figure 1. Location map of samples dated. Includes locations of samples not dated in this study (see Legend). The light gray represents the Bronson Hill terrane and the dark gray denotes the Avalon terrane. METHODS

Sample Preparation All samples were crushed, ground, and sieved to >250, 180, 150, 125, and <125 pm sizes. The largest size fraction that excluded most composite grains was selected for mineral separation by heavy liquids, magnetic separation and/or paper shaking. Composite grains were eliminated by ultrasonic abrasion where necessary. Purity to >99% of muscovite and biotite and 99.9% for amphibole was checked with a binocular microscope using reflected light. Approximately 1000 mg. of amphibole, 100 mg. of muscovite, and 50- 100 mg. of biotite were packaged in aluminum capsules and sealed under vacuum in quartz tubes. Samples were then irradiated in the central thimble facility at the TRIGA reactor (GSTR) at the U.S. Geological Survey, Denver, Colorado. The monitor mineral was MMHb-1 hornblende which has an age of 519.4 ± 2.5 Ma (Alexander et al., 1978; Dalrymple et al., 1981). The type of container, and the geometry of samples and standards is similar to that described by Snee et al. (1988).

Sample Analysis All samples were analyzed on a VG Isotopes, Ltd., Model 1200 B Mass Spectrometer at the U.S. Geological Survey, Reston, using the step heating method. Heating for 10 minutes per step followed a schedule of 8-15 steps per sample. The number and temperature of heating steps was selected to limit the percentage of gas released to less than 20%/step for most samples. Heating of all samples was done in a small volume molybdenum-lined "low blank" tantalum furnace. Temperature was monitored by a W5Re- W^Re thermocouple and controlled by a proportional, programmable controller. The furnace and the rear manifold were evacuated as necessary by a turbo molecular pump. Two isolated ion pumps evacuated the front manifold and the mass spectrometer tube. During normal operation, the gas to be analyzed was purified in the rear manifold by a Saes ST707 Zr-V-Fe getter operated at room temperature. Gas was equilibrated with the front manifold with an empty cold finger (in the rear manifold) chilled with liquid N2 to remove condensables (chiefly water), and cleaned in the front manifold by a Saes ST101 Al-Zr getter operated at 400°C and a Ti (H2) getter operated at a constant 350°C. An activated charcoal finger submerged in a constant boiling mixture of dry ice and acetone was used to remove gasses with a molecular weight greater than 60 or 80 (primarily noble gases) prior to the admission of the argon dominated gas to the mass spectrometer by expansion. The argon-rich gas was further purified in the mass spectrometer by a second Saes ST101 getter operated at room temperature. Its successful operation could be monitored by the drop in counts of mass 44 (dominated by GO2) after the first gas analysis cycle. All phases of the analysis; heating, gettering, equilibration, and mass spectrometer analysis were performed under computer control. Argon isotopes with masses 40 through 36 and GO2, mass 44 were analyzed as a function of time in five analysis cycles. 40Ar, MAr, and ^Ar peaks and their baselines, were measured as a series of four, five second integrations in each of the five cycles, that were then averaged. ^Ar and 37Ar peaks, and their baselines, were measured for only one, five second integration per cycle. After the analysis, the mass spectrometer was evacuated. If necessary, the fraction of gas remaining in the front manifold could be introduced into the mass spectrometer for a replicate "split" analysis, but with a signal 3.6 X smaller (see tables below).

Isotopic Data Reduction All the Ar isotopic data were reduced using an updated version of the computer program ArAr* (Haugerud and Kunk, 1988) and decay constants recommended by Steiger and Jager (1977). The isotopic measurements made in the five cycle analysis had baseline values subtracted and then were regressed, to time zero, using standard linear regression techniques. These regressed values and associated statistical estimates of analytical uncertainties of the time zero peak values were used in the data reduction. No corrections for furnace blanks were made because blanks were routinely less than 0.1% of sample signal at all temperatures. Corrections for interfering reactor-produced argon isotopes from Ga, K, and Gl in the sample were made using the production ratios given in Dalrymple et al. (1981). Errors included in calculating ages or ratios include analytical errors in the analysis, decay factor uncertainties, measured atmospheric or calculated initial ^Ar/^Ar ratios, the irradiation parameter J, the production ratios of the various reactor induced argon producing reactions, the inital ^Ar/^Ar ratio, and the age of the monitor (Haugerud and Kunk, 1988). In this project unique variables arise from the neutron flux as revealed through the calculated J values using Minnesota hornblende MMHb-1 (Alexander et al., 1978) and its age of 519.4 Ma ± 0.5%. Over 20 hornblende monitors were added to a single vial, and these defined a smooth curve where J varied from 0.0088 to 0.0098 across the six, 12 cm. long vials. Monitors were added to the top and/or bottom of each of the other five vials to assess any rotational fluctuation in the 6-vial package; none was found, within the limits of analytical precision. Sensitivities in moles ^Ar/count were calculated from analytical results on Minnesota hornblende MMHb-1 and its published composition (Alexander et al., 1978), and these sensitivity values are included in the data table for each sample. The tables and figures below include the identification of plateau ages, isochron ages, minimum ages, fusion ages and total gas ages. Plateau ages include two or more contiguous steps that overlap within experimental error, and whose cumulative MArK comprises greater than 50% of the total potassium derived MAr (Fleck et al., 1977; Snee et al., 1988). For all samples analyzed by the ^Ar/^Ar age spectrum dating technique, all steps were examined for colinearity on isotope correlation diagrams to assess if non-atmospheric argon components were trapped in any samples and to calculate an isochron age. In several samples points that were deemed to be not colinear were deleted from the isotope correlation diagram. Minimum ages are of a single step (except the first step in the age spectrum) and represent the lowest age measured in a U- or L- shaped spectrum. No analytical precision is stated for minimum ages in Table 1. Fusion ages represent the results of a single analysis in which all of the argon was released by melting in a single step. Total gas ages represent the age calculated from the addition of all of the measured argon peaks for all steps of a single sample. The total gas and fusion ages are equivalent to conventional K/Ar ages. No analytical precision is calculated for total gas ages. SAMPLE DESCRIPTIONS

The locations and descriptions of sample analyses in this project are given below. Petrographic observations were made on a single thin section cut perpendicular to foliation and parallel to lineation where present. In the descriptions that follow, minerals are listed in decreasing order of abundance. Because of their small size, quartz and plagioclase inclusions in larger mineral grains could not always be differentiated by use of the petrographic microscope. Descriptions focus on the minerals separated and dated.

92-112 42°25'30" N, 72°24'H" W Location: natural outcrop 800 m north of the intersection of Hwy. 202 with the Franklin Co./Hampshire Co. line, and 400m (0.25 mi) west of Hwy 202, on the west side of the hill at an elevation of ~ 1050 ft. in the Shutesbury 7 1/2' quadrangle, Massachusetts. Map Unit: Rocky Run Gneiss (Michener, 1983). Description: Buff, layered, quartz, plagioclase, biotite, epidote, sphene gneiss. Biotite grains range from 300 um. to 1.5 mm. The parallel alignment of biotite defines a weak foliation. Epidote grains range from 50 um. to 1.5 mm. in diameter. Many epidote grains contain quartz inclusions that are <200 um. in diameter. Only biotite was separated.

92-114 42°18'25" N, 72° 24' 18" Location: roadcut on the west side of Hwy. 202, 800 m north of the intersection of Hwy. 202 with Alien St. in the Belchertown 7 1/2' quadrangle, Massachusetts. Map unit: Fourmile Gneiss of the Geologic Map of the Pelham- Shutesbury Syncline, Pelham Dome (Michener, 1983). Description: Grey layered, plagioclase, hornblende, biotite, epidote, quartz gneiss. Hornblende grains are equant and range in size from 400 um. to 3 mm. long. Many amphibole grains contain plagioclase inclusions that range from <100 um. to 300 um. in diameter. A few amphiboles contain epidote and/or smaller amphibole inclusions: epidote inclusions are subhedral and range from <100 to 200 um. in diameter. Rare amphibole inclusions are subhedral and are up to 500 um. in length. Some amphiboles have rims of actinolitic composition. Biotite defines a foliation that truncates amphibole. Biotite grains range from ~300 um. to 3mm. long and some contain inclusions of plagioclase that are ~100 um. in diameter. Epidote grains range from ~200 um. to 1mm. in length. Only hornblende was separated.

8 92-115 42°15'43" N, 72°17'26" W Location: outcrop on the north side of H\vy. 9 , ~ 4 km west of the junction of Hwy. 32 and Hwy 9 at Brimstone Hill in the Winsor Dam 7 1/2' quadrangle, Massachusetts. Map unit: Amphibolite member of the Partridge Formation (Robinson et. ah, 1986). Description: Grey, hornblende, plagioclase, biotite, quartz, chlorite, granofelsic amphibolite. Most hornblende grains are equant and range from 500 um. to 3 mm. in diameter. Most hornblende grains contain inclusions of quartz and/or plagioclase that range from 100 um. to 500 um. in diameter. Biotite grains range from 300 um. to ~2 mm. in length and commonly crosscut hornblende and plagioclase and other biotite grains. Equant plagioclase and quartz grains range from 300 urn. to ~2 mm. in diameter. Hornblende and biotite were separated.

92-116 42°15"43" N, 72°17'26" W Location: outcrop on the north side of Hwy. 9 , ~ 4 km west of the intersection between Hwy. 32 and Hwy 9 at Brimstone Hill in the Winsor Dam 7 1/2' quadrangle, Massachusetts. Map unit: Partridge Formation (Robinson et. al., 1986, step #2). Description: Buff, plagioclase, quartz, biotite, muscovite pegmatite. Biotite books range from 1 to 5mm. thick. Only biotite was separated.

91-524 42°5'51" N, 72023'59" W Location: outcrop on east side of Glendale Rd., 1.5 km south of the intersection between Glendale Rd. and Monson Rd. and two miles east of the town of Wilbraham in the Hampden 7 1/2' quadrangle, Massachusetts. Map unit: Pegmatite in the Glastonbury Gneiss (Middle Devonian to Middle Ordovician) of the Hampden 7 1/2' quadrangle (Peper, 1977a). Description: Buff to white, coarse grained, plagioclase, K-feldspar, quartz, muscovite pegmatite. Muscovite books are ~3mm. thick. Muscovite was separated. 91-521 42°5'44" N, 72°19'28" W Location: an abandoned rock quarry just north of the intersection between Paradise Lake Rd. and Ely Rd. in the Monson 7 1/2' quadrangle, Massachusetts. Map unit: Monson Gneiss (Middle Ordovician or older) of the Monson 7 1/2' quadrangle (Peper, 1977b). Description: Black, hornblende, plagioclase, epidote, clinozoisite amphibolite. About 1/4 of the amphibole grains are elongated and others are equant. Elongated hornblende grains range in size from 1 to 4 mm. in length while equant grains range from 0.5 mm to 2 mm. in diameter. The elongated and equant hornblende grains are randomly oriented and are intergrown. Only a very few hornblende grains contain inclusions of plagioclase and/or quartz. These inclusions are <200 um. in diameter. Most plagioclase grains are euhedral and range from 0.5 mm. to 3.5 mm. in diameter. Twinning is noticeable in almost all plagioclase grains. Both epidote-clinozoisite occur with patches of plagioclase grains. Most epidote grains are euhedral and are ~200 um. in diameter. Glinozoisite grains range in length from 300 um. to 1.5mm. Only hornblende was separated. 42°5I34" N, 72°23'57" W Location: 3.2 km east of the town of Wilbraham, a roadcut on the west side of Glendale Rd., 2.4 km south of the intersection of Monson Rd. and Glendale Rd. in the Hanpden 7 1/2' quadrangle (Peper, 1977a). Description: Dark grey, foliated, hornblende, biotite, plagioclase, clinoziosite, epidote, quartz amphibolite. There are elongated hornblende grains and oval to round, anhedral hornblende porphyroblasts. The hornblende porphyroblasts range from 0.5 mm. to 2.5 mm. in diameter. Both the elongated hornblende grains and the hornblende porphyroblasts contain inclusions of quartz and/or plagioclase that range from <100 um. to 300 um. in diameter. A few of the larger porphyroblasts also contain inclusions of subhedral epidote, clinozoisite, and hornblende grains that are up to 500 um. long. The foliation wraps around the porphyroblasts. Elongated hornblendes range from 0.5 to 2 mm. long. Biotite grains also range from 0.5 to 2 mm. long. Epidote and clinozoisite are associated with biotite and most are zoned. Epidotes are subhedral and range from 100 to 300 um. in diameter. Glinozoisite grains are also subhedral and range from 100 um. to 1 mm. long. Plagioclase grains are equant and most are optically zoned. Hornblende and biotite were separated.

10 91-522 42°4'14" N, 72°21'15"W Location: natural outcrop on the west side of Wood Hill Rd. 300 m north of the intersection between Wood Hill Rd. and Lower Hampden Rd. in the Monson 7 1/2' quadrangle, Massachusetts.

Map unit: Littleton formation of the Monson 7 1/2'quadrangle (Peper, 1977b). Description: This rock is very similar to sample 91-529 except that this sample contains atolled garnets and staurolite grains ranging from 200 um to 3 mm. in length. Only muscovite was separated.

91-530 41°54'16" N, 72°26'42" W Location: Roadcut 2.3 km due east of the town of Ellington on the east side of Pinnacle Rd., 1.5 km north of its intersection with Shenipsit Lake Rd. in the Ellington 7 1/2' quadrangle, Connecticut. Map unit: Middletown Formation- pegmatite within the hornblende schist, Ellington 7 1/2' quadrangle (Gollins, 1954). Description: Buff to white, coarse grained, K-feldspar, plagioclase, quartz, muscovite pegmatite. Muscovite books are -4mm. thick. Muscovite was separated.

91-531 41°54'14" N, 72°26'47" W Location: Roadcut 1.8 km due east of the town of Ellington on the west side of Pinnacle Rd., 1.5 km north of its intersection with Shenipsit Lake Rd. in the Ellington 7 1/2' quadrangle, Connecticut. Map unit: Middletown Formation - hornblende schist member, Ellington 7 1/2' quadrangle (Collins, 1954). Description: Greyish green, well foliated, hornblende, plagioclase, quartz, epidote amphibolite. The foliation is defined by elongated hornblende grains ranging from 1 mm. to 3 mm. in length and from 200 to 500 um. in width. Many hornblende grains contain inclusions of quartz and/or plagioclase that are -50 to 100 um. in diameter. Quartz and plagioclase grains are also elongated and range from 0.5 mm. to 1.5 mm. in length. Epidote and clinozoisite grains are mostly subhedral and range from 200 um. to 1 mm. in length. Epidote and clinozoisite are randomly oriented and crosscut hornblende. Only hornblende was separated.

11 91-529 41052'41" N, 72°23'48" W Location: Natural outcrop in the southeast corner of the Ellington 7 1/2' quadrangle, 300m due east of Poehnarts Pond on the east side of the hill at an elevation of approximately 935 ft. Map unit: Bolton Schist of the Ellington 7 1/2' quadrangle (Gollins, 1954). Description: Buff to tan, strongly foliated, muscovite, biotite, quartz, plagioclase, garnet, staurolite, chlorite schist. This layered rock contains phyllosilicate dominated and quartz-dominated domains. These domains are discontinuous and vary in thickness from 2.0 mm. to 6.0 mm. In both domains the foliation is defined by muscovite and biotite. The phyllosilicate dominated domains are composed of 75% muscovite and biotite folia, 10% quartz grains, 5% biotite porphyroblasts, and 10% garnet and staurolite porphyroblasts. The quartz dominated domains contain 70% quartz, 15% muscovite and biotite folia, 5% staurolite, 5% garnet, and 5% biotite porphyroblasts. The muscovite and biotite grains that define the foliation range from 1 to 2mm. in length. This foliation wraps around the garnet, biotite, and staurolite porphyroblasts. The garnets are euhedral to subhedral and range from 1.5 to 4mm. in diameter; some have a few quartz inclusions. The biotite porphyroblasts are slightly elongated and range from 1 to 2.5 mm in length. Most staurolite porphyroblasts are elongated and range from 2 to 6 mm. in length. The quartz grains are slightly elongated and range from 300 um. to 1.5 mm. in length. Chlorite is usually associated with staurolite and crosscuts the porphyroblasts and the foliation. Muscovite and biotite were separated.

91-528 41°51'57" N, 72°2r42" W Location: Northeast end of parking lot north of intersection of 186 with Conn. Route 195 in the South Coventry 7 1/2' quadrangle, Connecticut. Map unit: Monson Gneiss of the South Coventry 7 1/2' quadrangle (Fahey and Pease, 1977). Description: Dark grey, finely layered, plagioclase, quartz, hornblende, biotite, epidote, clinozoisite gneiss. Hornblende, biotite, epidote, and clinozoisite occur in layers separated by quartz and plagioclase rich layers. Plagioclase and quartz grains are equant and range from 300 pm. to 1 mm in diameter. Some plagioclase grains contain inclusions of quartz, and veins of quartz from 1 to 2 mm. in width and ~lcm. long are present. Hornblende grains are subhedral to anhedral and sides parallel to the cleavage of hornblende are commonly straight in some grains, in other grains the hornblende grain boundaries are

12 strongly serrated and interlobate with adjacent plagioclase grains. The hornblende grains range from 300 pm. to 2 mm. in diameter. Many hornblende grains contain plagioclase, quartz inclusions ranging from 100 to 500 pm. in diameter. Biotite grains define a weak foliation and range from 300 pm. to 1 mm. in length. Some epiodote grains contain inclusions of quartz that are -100 pm. in diameter. Hornblende and biotite were separated.

91-533 41°48'08" N, 72°24'34" W Location: 1.1 km north of the northern tip of Bolton Notch Pond and 150m west of Railroad Brook at the noil of elevation 660 ft. in the Rockville 7 1/2' quadrangle, Connecticut. Map unit: Bolton Schist-"quartzitic phase" of the Rockville 7 1/2' quadrangle (Aitken, 1955). Description: Grey to tan, hornblende, quartz, biotite, clinozoisite, garnet plagioclase, chlorite amphibolite. Hornblende grains range from 100 pm. to 0.5 mm. in diameter. Most contain quartz and/or plagioclase inclusions that are less than 100 pm. in diameter. Equant quartz and plagioclase grains range from 100 pm. to 400 pm. in diameter. Subhedral to anhedral garnets range from 300 pm. to 2 mm. in diameter. Most garnets contain quartz inclusions from 100 to 300 pm. in size. Biotite grains range from 300 pm. to 700 pm. in length. Chlorite occurs near garnet. Garnet crosscuts all adjacent grains. Garnet concentration may exceed 50% in some layers where garnets are as large as 3.5 mm., and amphiboles are up to 2 mm. long. Clinozoisite grains are subhedral and occur in areas where there is no garnet. Only hornblende was separated.

88-328 41042'26" N, 72029'25" W Location: Contact metamorphic zone around metagranite intruding Glastonbury gneiss (Ambers, 1988) 300 m. south of Connecticut Route 94, 1.6 km west of the contact between the Glastonbury dome and Clough quartzite in the Marlborough 7 1/2' quadrangle, Connecticut. Map unit: Glastonbury Gneiss of the Marlborough 7 1/2' quadrangle (Snyder, 1970). Description: Hornblende, biotite, quartz, epidote, plagioclase, clinozoisite, microcline, sphene hornfels. The hornblende, biotite, epidote, and clinozoisite occur in layers separated by quartz and plagioclase rich layers. A weak foliation is defined by biotite. Hornblende grains are subhedral and some are slightly elongated and range from 1 to 4 mm. in length. Some

13 hornblende grains have quartz, plagioclase, and/or biotite inclusions. The quartz and plagioclase inclusions range from 100 to 300 pm. in diameter and the biotite inclusions range from 200 to 500 um. in length. The biotite grains range from 500 um. to 1.5 mm in length. Quartz and plagioclase grains are equant and range from 400 um. to 1.5 mm. Small anhedral microcline is associated with quartz and plagioclase. Both epidote and clinozoisite are subhedral and range from 200 um. to 800 um. in length. Many epiodte and clinozoisite grains are zoned. Euhedral to subhedral sphene is associated with biotite and epidote. Only hornblende was separated.

88-330 41°40'53" N, 72°33'19" W Location: Collected from an excavation around an electrical substation on the south face of a hill 50 m. north of Chestnut Hill Rd., 300 m. west of its intersection with the New London turnpike in the Glastonbury 7 1/2' quadrangle, Connecticut. Map unit: Glastonbury Gneiss of Glastonbury 7 1/2' quadrangle (Herz, 1955). Description: Quartz, plagioclase, biotite, epidote, hornblende, gneiss. Some quartz and plagioclase grains are over 1cm. in diameter. These large grains sometimes contain inclusions of smaller quartz or plagioclase grains. Other quartz and plagioclase grains range from 200 um. to 1 mm. in diameter. Biotite, epidote, and hornblende occur in layers separated by plagioclase and quartz. Biotite defines a weak foliation. Biotite grains range from 200 um. to 1.5 mm. in length. Subhedral epidote grains range from 100 pm. to 400 um. in diameter. Hornblende grains are somewhat elongated and grain boundaries are commonly serrated and interlobate with adjacent plagioclase or quartz grains. Hornblende grains range from 0.5 to 1.5 mm. in length. Most hornblende grains contain epidote inclusions that are <200 pm. in diameter. Only hornblende was separated.

88-331 41°39T'N, 72029'39" W Location: Exit ramp off of eastbound Connecticut Route 2 at Portland Rd., 3.2 km east of Marlborough village in the Marlborough 7 1/2' quadrangle, Connecticut. Map unit: Monson Gneiss of Marlborough 7 1/2' quadrangle (Snyder, 1970). Description: Hornblende, plagioclase, quartz, epidote, biotite, granofelsic amphobilite. Hornblende grains are subhedral to anhedral and sides parallel to the cleavage of the hornblende are commonly straight in some grains, in other grains the grain boundaries are

14 strongly serrated and interlobate with adjacent plagioclase grains. The hornblende grains range from 300 um to 1.5 mm in diameter. Many hornblende grains contain quartz and/or plagioclase inclusions 100 to 300 urn. in diameter. Equant plagioclase and quartz grains range from 300 um. to 1 mm. in diameter. Most epidote grains are subhedral and -300 um. across. Biotite distribution is patchy, and grains range from 400 um. to 1 mm. in length. Only hornblende was separated.

91-543 41°29'45" N, 72°34'19" W Location: twelve cm. thick amphibolite in a plagioclase gneiss outcrop on the west side of Route 9, under the overpass of Christian Hill Rd., 3.2 km west of Higganum in the Haddam 7 1/2' quadrangle, Connecticut. Map unit: Monson Gneiss of the Haddam 7 1/2' quadrangle (Lundgren, 1979). Description: Grey layered, hornblende, plagioclase, quartz, biotite amphibolite. Most hornblende grains are elongated and range from 1 to 6 mm. in length. Some hornblende grains have quartz and/or plagioclase inclusions that are approximately 50 to 150 um. in diameter. Plagioclase grains are 200 um. to 1 mm. in diameter. Some plagioclase grains show optical zoning. Hornblende grains appear in layers separated by plagioclase layers. Minor biotite crosscuts the banding. Hornblende was separated.

92-111 41°26'44" N, 72°39'49" W Location: roadcut on the west side of Hwy. 79, 110 m north of the intersection between Hwy. 79 and Pisgah Rd., 800 m north of the Killingworth/Durham town line in the Durham 7 1/2' quadrangle, Connecticut. Map unit: Pegmatite cutting Brimfield, Collins Hill Formation (Rodgers, 1985). Description: Buff, coarse grained, K-feldspar, plagioclase, quartz, muscovite pegmatite. Muscovite books are ~5 mm. thick. Only muscovite was separated.

15 92-109 41°23T' N, 72°26'59" W Location: Southbound exit ramp at interchange 5 Conn. Route 9 in the Deep River 7 1/2' quadrangle, Connecticut. Map unit: Pegmatite cutting Monson Gneiss of Deep River 7 1/2' quadrangle (Lundgren, 1963). Description: Buff, plagioclase, quartz, biotite, zircon pegmatite. Biotite books range from 0.5 to 7 mm. thick. Only biotite was separated.

90-153 41°23T N, 72°26'59" W Location: Southbound exit ramp at interchange 5 Conn. Route 9 in the Deep River 7 1/2' quadrangle, Connecticut. Map unit: Middletown Formation of Deep River 7 1/2' quadrangle (Lundgren, 1963). Description: Black hornblende-plagioclase-epiodite massive amphibolite. Hornblende grains are 1-5 mm in diameter, with intersticial plagioclase 0.5-1.0 mm in diameter. Only hornblende was separated.

92-110 41°21'38" N, 72°38'15" W Location: roadcut 60 m northeast of the intersection (roundabout) between Hwy. 80 and Hwy 79 at North Madison in the Guilford 7 1/2' quadrangle, Connecticut. Map unit: Monson Gneiss (Rodgers, 1985). Description: Hornblende, plagioclase, garnet, weakly layered, gneiss. Most hornblende grains are elongated and have grain boundaries that are serrated and interlobate with adjacent plagioclase grains. Hornblende grains range from 300 um. to 3 mm. in length. A few hornblende grains contain inclusions of plagioclase that are ~100 mm. in diameter. Equant plagioclase grains range from 200 um. to 2 mm. in diameter, and most show optical zoning. Minor garnet (some a toll-shaped) occurs only in small layers; most range from 100 to 600 pm. in diameter and are in contact with hornblende. Rare garnet is 2 mm. and contains many quartz inclusions. Only hornblende was separated.

16 92-122 41°19'55" N, 72042'24" W Location: outcrop on east side of Hwy. 77 (north of Interstate 95), 1.8 km north of Stepstone Hill Rd. in the Guilford 7 1/2'quadrangle, Connecticut. Map unit: Middletown or Collins Hill Formation (Rodgers,1985). Description: Black, well foliated, hornblende, quartz, plagioclase amphibolite. Elongated amphibole grains make up -90% of the rock and range in size from 1mm. to 1cm. in length and from 300 pm. to 1 mm. in width. Some of the hornblende grains have quartz and plagioclase inclusions that are approximately 100 pm. in diameter. Quartz and plagioclase grains are not equant and range in size from 300 pm. to 1.5 mm. Only hornblende was separated.

91-550 41°18'59" N, 72026'2" W Location: roadcut on east side of Brook Plains Rd. 2.9 km north of interchange 65 in the Essex 7 1/2' quadrangle, Connecticut. Map unit: Monson Gneiss of the Essex 7 1/2' quadrangle (Lundgren, 1964). Description: Dark to light gray, layered, quartz, plagioclase, hornblende, biotite, magnetite, gneiss. Equant quartz and plagioclase grains range from 200 pm. to 1.5 mm. in diameter. Some plagioclase grains show optical zoning. Hornblende grains are subhedral to anhedral. The sides parallel to the cleavage of the hornblende grains are commonly straight in some grains, in other grains the grain boundaries are strongly serrated and interlobate with adjacent plagioclase grains. Hornblende grains range from 200 pm. to 4 mm. long. Some of the hornblende grains have quartz inclusions that are approximately 200 to 400 um. in diameter and many are crosscut by biotite grains. Most hornblende grains occur in aggregates separated by plagioclase and quartz. Biotite grains range from 200 pm. to 2mm. in length and define a moderate foliation sub parallel to layering. About 10% of biotite grains are randomly oriented and crosscut the foliation. Hornblende and biotite were separated.

17 92-107 41°17'55" N, 72°48'15" W Location: natural outcrop on the north side of Short Rocks Rd. (northern side of Interstate 95), just 120 m east of the intersection between Short Rocks Rd. and Chestnut St. (where Chestnut St. goes between the Branford Supply Ponds) at an elevation of 15 m in the Branford 7 1/2' quadrangle, Connecticut. Map unit: Branford Gneiss (Rodgers, 1985). Description: Dark grey, hornblende, plagioclase, epidote, granofelsic amphibolite. Hornblende grains are equant and commonly have serrated grain boundaries that are interlobate with adjacent plagioclase grains. Hornblende grains range from 500 pm. to 2 mm. in diameter. Most hornblende grains contain inclusions of plagioclase that range from 100 to 600 pm. in diameter. Plagioclase grains are equant and range from 300 pm. to 1.5 mm. in diameter. Minor epidote grains are -300 pm. in diameter. Only hornblende was separated.

91-548 41°17'43" N, 72°42'18" W Location: roadcut on the northeast side of route 460 m south of 1-95 Interchange 57 in the Guilford 7 1/2' quadrangle, Connecticut. Map unit: Waterford Group (Rodgers, 1985). Description: Hornblende, plagioclase, biotite, garnet, quartz amphibolite. Hornblende grains range from 300 pm. to 1mm. in diameter. Some hornblende grains contain quartz and/or plagioclase inclusions <200 pm. in diameter. Equant plagioclase and quartz grains range from 300 pm. to 1mm. in diameter. Most plagioclase grains are optically zoned. Anhedral garnets occur in a layer and range from 1 mm. to 3 mm. in diameter. These garnets contain many quartz inclusions that range from 100 to 600 pm. in diameter. Biotite flakes range from -300 pm. to 1.5 mm. long. Biotite flakes occur throughout the slide, but are most numerous within the garnet-rich layer where they commonly crosscut garnet. Hornblende and biotite were separated.

92-103 41°17'43" N, 72°42'18" W Location: roadcut on the northeast side of route 460 m south of 1-95 Interchange 57 in the Guilford 7 1/2' quadrangle, Connecticut. Map unit: Monson Gneiss (Rodgers, 1985). Description: Buff to white, coarse grained, K-feldspar, plagioclase, quartz, muscovite pegmatite. Muscovite books are -0.5 cm. thick. Muscovite was separated.

18 92-102 41°17'25" N, 72°33'44" W Location: Roadcut located northeast of the intersection of 1-95 and hwy 81 (interchange 62), just 30 m east of the Nodd Rd. square near the junction with River Rd. in the Clinton 7 1/2' quadrangle, Connecticut. Map unit: Monson Gneiss of Clinton 7 1/2' quadrangle (Lundgren and Thurrell, 1973). Description: Medium gray, massive, quartz, plagioclase, hornblende, biotite, magnetite gneiss. Equant quartz and plagioclase grains range from ~200 pm. to 1.5 mm. in diameter. Hornblende grains are subhedral to anhedral. Sides parallel to the cleavage of the hornblende are commonly straight in some grains, in other grains the hornblende grain boundaries are strongly serrated and interlobate with adjacent plagioclase grains. Hornblende grains range from 200 pm. to 2.5 mm. long. Most of the hornblende grains have quartz and/or plagioclase inclusions that are 200 to 700 mm. in diameter. Most hornblende grains occur in aggregates separated by plagioclase and quartz. Biotite grains range from ~200 pm. to 2.0 mm. in length and some crosscut hornblende grains. Only hornblende was separated.

92-104 41°14'3r' N, 72°53'39" W Location: natural outcrop collected at South End on the southeastern promentory of Morgan Point in the Woodmont 7 1/2' quadrangle, Connecticut. Map unit: Light house Gneiss (Rodgers, 1985). Description: Biotite books ~1 cm. thick were collected from a granite. Thin section not available.

19 RESULTS

40Ar/^Ar Data

The 4QArP9Ar data, presented in this report are presented in two different formats. Data within both formats are arranged in the same order as the section on sample descriptions, from north to south. The first of these formats is a condensed tabular form (Table 1). These tables summarize the data contained in the succeeding, more detailed individual data sets. Included in this table are: the sample numbers; the material analyzed, the apparent age and its error (see below for a detailed explanation); the percent 39Ar of the total that this apparent age represents; the number of steps/total number of steps that this apparent age represents; the MSWD, for isochron ages; the initial 40Ar/36Ar used in calculating the apparent age (or atmos. if 295.5 was used); and a comment listing the type of apparent age. The individual data sets include a series of four tables, as well as three graphical representations of some of the age spectrum data. Total fusion analyses have no figures. The first table, RAW DATA, includes the computer file number of the individual argon analysis, the temperature of the step, regressed peak values and their precision, the trap current (filament amperage, in microamps) and the manifold splitting option used. The relationship between the trap currents and manifold options can be found in the footnotes of the third table. No corrections have been made to the peak values, these are raw numbers. The second table, CORRECTIONS, contains calculated corrections for decay of radioactive isotopes of argon, as well as the production of interfering isotopes during irradiation and, a calculated initial 38Ar value. All of these values have been corrected only for the affects of mass discrimination as discerned by measuring atmospheric argon. The measured atmospheric argon value used is listed in the footnote of table three. All tabular data in this table, as well as the two subsequent tables, is indexed by the temperature of the step analyzed. The third table includes the percent 39Ar of the age spectrum total that each step contains, the radiogenic yield (percentage of 40Ar that is derived from the decay of potassium), calculated apparent K/Ca and K/C1 ratios for each step, a corrected 40Ar/39Ar ratio (labeled F) from which the age can be directly calculated, a calculated age for the step, in millions of years and a series of three estimates of the precision of each age. The intra- sample precision includes estimates of the errors that are unique to a single sample and can be used only for comparisons with other steps of the same sample. The intra-package precision includes an estimate of the precision of

20 the irradiation parameter J and can be used to compare total fusion analyses that used the same monitor mineral. This estimate of precision should not be used to compare steps either within a single age spectrum or between different age spectra. The inter-package precision includes an estimate of the precision of the age of the monitor mineral and should not be used for comparisons of any data contained in this report. Also included, as a footnote, is an estimate of the limit of reproducibility of the mass spectrometer when the sample was analyzed. If an intra-sample error is less than this value times the age of the step, this value should be used when comparing with other steps from the same age spectrum. The fourth data table lists molar quantities of the indicated argon isotope derived from the sources indicated. The age and the estimate of intra-sample precision are repeated. The J-value and its precision estimate, and sample weight are listed near the top of this table. If an age plateau, as defined above, was found, it is listed at the bottom of this table along with an estimate of its intra-package precision, the percent 39Ar contained in the plateau and the temperatures of the first and last steps on the plateau. All precision estimates, in ail tables, are at the one sigma level of confidence. The first figure with each age spectrum data set includes two graphs. The lower and larger graph plots cumulative percent 39Ar of the steps in the age spectrum against apparent age in millions of years. The precision estimate used to construct the error boxes of each step is two sigma. The upper, smaller graph plots the apparent K/Ca ratio of each step against cumulative 39Ar released. Many times the degree of sample purity or the presence of compositional zoning can be inferred from this figure. Homogeneous samples with no compositional zoning or impurities are reflected by horizontal patterns in this figure, the patterns of those with zoning or impurities typically depart from horizontal. All hornblende age spectra data sets have a third figure included, an inverse isotope correlation diagram. In this figure the corrected 39Ar/40Ar ratio of each temperature step of an age spectrum is plotted against its corrected 36Ar/40Ar ratio. The intercept of the line generated by these points with the X-axis of the graph is the inverse of the 40Ar/39Ar ratio of those points included on the line, and an age can be directly calculated from this value. The Y-axis intercept is the inverse of the initial 40Ar/36Ar ratio of the sample. This value can be used to indicate the presence of excess argon. Values for these intercepts and their inverse ratios as well as their errors can be found either above or below this figure. Also included are an age calculated from the inverse of the X-axis, an MSWD, for the points included in the calculations, a list of points that were not used in the regression and the percent 39Ar included in the line. For additional information on the sample datasets see Haugerud and Kunk (1988).

21 TABLE 1. Summary of argon isotopic results from the Bronson Hill terrane

SAMPLE MIN AGE V'Ar STEPS MSWD 40Ar/36Ar COMMENT (Ma) TOTAL

92-112 Bi 243 100 1/1 atmos . total fusion 92-114 Hb 288,8 15.1 3/10 0.024 728,152 isochron 297 14.6 1/10 atmos . minimum 92-115 Hb 330,2 65.6 4/5 3.01 291,5 isochron 329 10.1 1/5 atmos minimum 92-116 Bi 259 100 1/1 atmos . total fusion 91-524 Mu 252,2 98.7 8/9 0.515 408,68 isochron 252 12.7 1/9 atmos minimum 91-521 Hb 314,4 78.0 3/8 0.554 690,94 isochron 310 2.9 1/8 atmos minimum 91-523 Hb 346,2 81.6 3/7 atmos . plateau 345,2 91.0 4/7 1.06 327,54 isochron Bi 290 100 1/1 atmos total fusion 91-522 Mu 251,6 47.2 4/9 1.95 521,398 isochron 250 6.8 1/9 atmos minimum 91-530 Mu 252,1 90.1 3/4 atmos . plateau 252,8 90.1 3/4 0.021 340.939 isochron 91-531 Hb 294,1 66.6 3/5 atmos . plateau 293,6 66.6 3/5 0.571 308,262 isochron 91-529 Mu 250,1 100 8/8 0.579 414,35, isochron 252 12.7 1/9 atmos minimum Bi 280 100 1/1 atmos . total fusion 91-528 Bi 255 100 1/1 atmos . total fusion 91-533 Hb 268, 1 51.8 2/4 atmos plateau 263,18 78.2 3/4 2.50 540,590 isochron 88-328 Hb 273,3 99.3 11/13 0.428 546,117 isochron 271 12.0 1/13 atmos minimum 88-330 Hb 274,3 97.7 10/13 0.91 268, 80 isochron 272 12.0 1/13 atmos minimum 88-331 Hb 265, 1 100 9/9 32.07 483,16 isochron 264,1 14.5 1/9 atmos minimum

22 TABLE l.(Gont.) Summary of argon isotopic results from the Bronson Hill terrane

SAMPLE MIN AGE %3JAr STEPS MSWD 40Ar/36Ar COMMENT (Ma) TOTAL

91-543 Hb 272,4 100 9/9 2.05 1028,263 isochron 268 13.1 1/9 atmos minimum 92-111 Mu 242,1 100 5/5 atmos . plateau 242,2 100 5/5 0.071 325,29 isochron 92-109 Bi 248 100 1/1 atmos . total fusion 90-153 Hb 245,7 92.2 7/8 0.814 295,306 isochron 92-110 Hb 257,1 54.8 3/4 atmos . plateau 257,1 54.8 3/4 5.37 294,2 isochron 92-122 Hb 252,1 100 4/4 atmos . plateau 251,2 100 4/4 0.051 300,4 isochron 91-550 Hb 258,1 99.0 7/8 atmos . plateau 257,2 99.0 7/8 0.035 344,94 isochron Bi 256 100 1/1 atmos total fusion 92-107 Hb 263,1 58.2 3/6 atmos plateau 262,1 82.0 5/6 0.856 298,7 isochron 91-548 Hb 249,1 82.3 3/8 0.075 359,9 isochron 247 2.8 1/8 atmos minimum Bi 252 100 1/1 atmos . total fusion 92-103 Mu 243,1 58.9 7/8 atmos . plateau 243,1 58.9 7/8 0.581 304,6 isochron 92-102 Hb 259,1 79.1 5/9 atmos plateau 259,3 79.1 5/9 0.006 328,202 isochron 92-104 Bi 242 100 1/1 atmos total fusion

23 v 06/13/92 92-112 #50 RD91 05:59:40 !3 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34845 1450 2061213 129042 3756 12 107 100 EALL 2641 147 6 14 3

CORRECTIONS

TEMP 39Ar 37Ar K-derived Ca-derived Cl-der Initial C Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1450 82 61 734 1732 20

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 1450 100,0 98.5 915.60 153 15.700 242.62 .31 1.18 1.64 Total gas K/Ca = 915.6

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 -.5 J = 0.009169 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.67 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.1167 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.0E-03

92-112 #50 RD91

J = 0.009169 « 0.50% SAMPLE WT = 0.0501 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar ' 38Ar 37Ar 36Ar in Ma

1450 1.454E-10 9.119E-12 1.447E-13 5.179E-15 7.530E-15 242.62 .31

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** l-al4fina precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproduc ibi1ity. *** below detection limit v 06/13/92 v 06/13/92 92-114 #26,27,28,29 RD91 01:31:59 19 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34690 1025 813795 39460 2265 42868 189 200 EALL , 544 21 5 61 7 34691 1050 344829 15593 1010 24462 109 200 EALL 157 11 21 41 6 34692 1075 435555 20224 1332 31045 126 200 EALL 248 15 9 33 3 34693 1100 1149117 57084 3606 107573 272 200 EALL 1175 82 8 201 6 34694 1125 3564822 178039 11999 238745 480 200 EALL 2329 153 9 150 3 34695 1150 1753684 89685 6444 85432 191 200 EALL 701 47 6 106 7 34696 1175 564200 27088 1944 30992 110 200 EALL 176 26 22 42 8 34697 1200 1141019 54528 3884 64924 158 200 EALL 620 46 8 108 7 34698 1250 2527931 121751 8842 131345 286 200 EALL 1171 77 9 104 7 34699 1350 264633 12401 813 16244 40 200 EALL 97 8 13 9 5

C 0 R R E C T IONS

TEMP 39Ar 37Ar ed Ca-derived Cl-der Initial |c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1025 24 192183 224 527 0 159 7 62 0 24 1050 9 109726 88 208 0 91 4 36 0 14 1075 12 139331 114 270 0 115 5 45 0 15 1100 34 483045 322 761 0 398 19 156 0 22 1125 107 1072633 1008 2377 0 885 42 347 2 25 1150 54 384033 508 1199 0 317 15 124 1 12 1175 16 139389 153 362 0 115 5 45 0 12 1200 33 292160 309 729 0 241 11 95 1 12 1250 74 591372 690 1627 0 488 23 191 1 18 1350 7 73177 70 166 0 60 3 24 0 3

All values in counts, corrected for mass discrimination

25 v 06/13/92 92-114 #26,27,28,29 RD91 01:32:01 19 Jan 1993

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/Cl (Ma) sample package package

A 1025 6.4 95.4 .09 54 19. 716 302. 30 .75 1.59 2.11 B 1050 2.5 93.7 .06 46 20. 808 317. 65 1.51 2.11 2.56 C 1075 3.3 94.5 .06 45 20. 436 312. 44 .57 1.55 2.11 D 1100 9.2 97.0 .05 48 19. 632 301. 12 .56 1.50 2.05 E 1125 28.9 98.9 .07 45 19. 867 304. 43 .20 1.42 2.00 F 1150 14.6 98.9 .10 41 19. 370 297. 41 .34 1.42 1.97 G 1175 4.4 96.6 .08 41 20. 170 308. 71 1.22 1.87 2.35 H 1200 8.9 98.4 .08 42 20. 638 315. 28 .52 1.54 2.12 I 1250 19.8 98.9 .09 41 20. 581 314. 47 .27 1.47 2.06 J 1350 2.0 98.2 .07 46 21. 023 320. 66 1.83 2.35 2.77 Total gas K/Ca .1

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 -.5 J = 0.009253 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.07 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295,50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03

J = 0.009253 0.50% SAMPLE WT = 1.0003 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* ** C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1025 2.484E-11 1.202E-12 5.368E-14 7.195E-12 3.883E-15 302.30 .75 1050 1.053E-11 4.740E-13 2.483E-14 4.108E-12 2.241E-15 317.65 1.51 1075 1.330E-11 6.149E-13 3.280E-14 5.215E-12 2.468E-15 312.44 .57 1100 3.508E-11 1.733E-12 8.714E-14 1.808E-11 3.544E-15 301.12 .56 1125 1.088E-10 5.417E-12 2.939E-13 4.014E-11 4.049E-15 304.43 .20 1150 5.353E-11 2.733E-12 1.604E-13 1.437E-11 2.028E-15 297.41 .34 1175 1.722E-11 8.248E-13 4.860E-14 5.215E-12 1.983E-15 308.71 1.22 1200 3.483E-11 1.660E-12 9.657E-14 1.093E-11 1.932E-15 315.28 .52 1250 7.716E-11 3.708E-12 2.206E-13 2.212E-11 2.886E-15 314.47 .27 1350 8.078E-12 3.773E-13 1.981E-14 2.737E-12 * ** 320.66 1.83 TOTAL 3.834E-10 1.874E-11 1.038E-12 1.301E-10 2.551E-14 307.03 GAS

NO PLATEAU

Note: all gas quantities are in moles. No blank correction. * Acjejp calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigtna precision estimates are for intra-sample reproducibility. ** 1-sigtna precision estimates for plateaux are for intra-irradiation package reproduc ib i1ity. *** below detection limit

/i v 06/13/92 01:33:04 19 Jan 1993 92-114 #26,27,28,29 RD91

.1 L

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i i 39ArK RELEASED (%} 2? 100

v 06/13/92 (40/36in = 295.5) X v 06/13/92 02:33:32 19 Jan 1993 92-114 £26,27,28,29 RD91 Points AEFGHIJ deleted; 3 points regressed out of 10 includes 15.1 % of 39Ar Mean X = .468E-01 Mean Y = .170E-03 Slope = -.257E-01 a+£ .615E-02 36/40 = .137E-02 a+£ .288E-03 39/40 = .534E-01 a+? .164E-02 Fit parameters: SUMS = .024 MSWD = .024 40Ar/36Ar = 728.16 a+£ 152.48 F = 18.737 a+ .575 AGE = 288.43 a+ 8.28 Ma

92-114

CO

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LO I

28 .009 .018 .027 .036 ,045 .054 39 ArrA ~ / 40i W/0 POINTS AEFGHIJ v 06/13/92 92-113 #45 RD91 03:27:07 21 Jan 1993

RAW DATA

TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34789 1100 2827809 108473 3553 240601 1705 200 EALL 1180 55 11 133 13 34790 1125 2172369 94858 2886 202106 972 200 EALL 4830 233 20 418 5 34791 1225 1471417 58614 1886 126292 994 200 EALL 2937 89 6 203 9 34792 1350 851101 31925 1058 70131 740 200 EALL 239 12 14 42 4 34793 1650 671048 21865 778 48188 811 200 EALL 649 45 5 69 4

CORRECTIONS

39Ar 37Ar K-derived - Ca-derived Cl-der Initial Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1100 69 1191670 612 1443 0 966 46 379 0 249 1125 60 1001539 535 1262 0 812 38 319 0 123 1225 37 626171 331 780 0 508 24 199 0 149 1350 20 347900 180 425 0 282 13 111 0 118 1650 14 239174 123 291 0 194 9 76 0 138

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) s ample package package

A 1100 34.4 86.1 .04 112 22. 606 351 .99 .53 1.70 2.34 B 1125 30.0 91.1 .04 133 21. 000 329 .13 .76 1.70 2.27 C 1225 18.6 84.0 .04 114 21. 228 332 .40 .96 1.81 2.37 D 1350 10.1 78.1 .04 104 20. 959 328 .55 .60 1.64 2.23 E 1650 6.9 67.5 .04 85 20. 864 327 .19 .93 1.80 2.34 Total gas K/Ca = 0.0

Precisions are 1 sigma/ measured in Ma. Measured 40/36 atm = 296.5 -.5 J = 0.009531 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.1167 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 29 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03 v 06/13/92 03:27:11 21 Jan 1993 92-115 #45 RD91

J = 0.009531 0.50% SAMPLE WT = 0.0997 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1100 8.827E-11 3.362E-12 7.244E-14 4.483E-11 4. 156E-14 351.99 .53 1125 6.781E-11 2.941E-12 5.348E-14 3.767E-11 2.049E-14 329.13 - .76 1225 4.593E-11 1.817E-12 3.856E-14 2.355E-11 2.491E-14 332.40 - .96 1350 2.657E-11 9.894E-13 2.310E-14 1.308E-11 1.973E-14 328.55 - .60 1650 2.095E-11 6.776E-13 1.927E-14 8.995E-12 2.304E-14 327.19 .93 TOTAL 2.495E-10 9.786E-12 2.068E-13 1.281E-10 1.297E-13 337.43 GAS

NO PLATEAU

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit

v 06/13/92

30 v 06/13/92 05:10:22 23 Jan 1993 92-115 #45 RD91

.1 c

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.01

350

ro

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cu c_ ro CZL 92-115 CZL HORNBLENDE 250

200 I I I I 39 0 An, RELEASED (%} 31 100

v 06/13/92 (40/36in = 295.5) v 06/13/92 03:30:58 21 Jan 1993 92-115 #45 RD91

Point A deleted; 4 points regressed out of 5 includes 65.6 % of 39Ar Mean X = .395E-01 Mean Y = 573E-03 Slope = -.724E-01 a+g 152E-02 36/40 = .344E-02 a+g .604E-04 39/40 = .474E-01 a+g .185E-03 Fit parameters: SUMS = 6.029 MSWD = 3.014 40Ar/36Ar = 291.1 a+g 5.11 F = 21.089 a+g .082 AGE = 330.41 a+g 1.92 Ma

92-115

OJ c_ S

CO m

32 .008 .016 .024 .032 .04 39 Ar/ 40Ar W/0 POINTS A v 06/13/92 92-116 #52 RD91 06:19:14 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34846 1450 2794251 163657 3486 72 200 40 EALL 2067 60 7 8 6

CORRECT IONS

TEMP 39Ar 37Ar K-derived Ca-derived - Cl-der Initial C Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1450 105 363 931 2196 37

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 1450 100.0 97.9 195.49 297 16.682 259.17 .23 1.23 1.73 Total gas K/Ca = 195.5

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 -.5 J = 0.009261 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 2.26 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.67 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.1167 ESPLIT 1: 7.77 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03

J = 0.009261 0.50% SAMPLE WT = 0.0498 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1450 1.971E-10 1.156E-11 9.409E-14 3.076E-14 1.411E-14 259.17 .23

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. 33 ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproduc ib i1ity. *** below detection limit v 06/13/92 91-524 #24 RD87 MUSCOVITE 16:46:36 , 28 Aug 1,992 32734 v 06/13/92 91-524 #24 MUSCOVITE RD87 15:19:04 28 Aug 1992

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD regression CURRENT OPTION

32723 900 185910 10521 73 28 42 20 0 EALL ± 289 20 16 21 2 32724 950 309367 17748 116 34 40 200 EALL ± 205 9 10 17 6 32725 1000 738525 41426 532 38 130 20 0 EALL ± 1161 50 18 9 4 32726 1050 2576420 148287 1914 0 234 20 0 EALL ± 994 47 4 9 6 32727 1100 4098421 244758 3093 4 135 2C 0 EALL t 5012 240 12 40 4 32728 1150 1742376 103505 1330 110 97 20 0 EALL t 225 16 5 13 2 32729 1200 1148447 66579 864 127 101 20 0 EALL ± 1064 74 9 8 6 32730 1250 1583996 93121 1193 88 77 20 0 EALL t 757 39 6 10 7 32731 1450 1490464 88320 1131 1183 31 20 0 EALL ± 716 40 18 8 7

C 0 R R E C T I 0 N S

TCUOI cnf 39Ar 37Ar -----K-derived------Ca-derived---- Cl- der Initial °C Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36 Ar 38Ar

900 3 30 60 141 0 000 -0 8 950 5 37 101 238 0 000 -0 8 1000 11 41 236 556 0 000 0 24 1050 38 0 843 1989 0 000 -0 44 1100 63 4 1392 3283 0 000 -0 25 1150 27 120 589 1388 0 000 -0 18 1200 17 138 379 893 0 000 -0 19 1250 24 95 530 1249 0 000 -0 14 U50 23 1286 502 1185 0 2 0 1 -0 6

All values in counts. corrected for mass discriminatior

34 v 06/13/92 91-524 #24 MUSCOVITE RD87 15:19:06 28 Aug 1992

pr ecision TEMP % TOT RAD APR APP F AGE intra- ir tra- inter- C 39Ar YIELD K/Ca K/Cl (Ma) sample package package

A 900 1.3 93.3 95.20 0 16.465 250.70 ± .92 1. 49 1 .90 B 950 2.2 96.1 129.97 0 16.735 254.54 ± 1.35 1. 80 2 .16 C 1000 5.1 94.8 272.38 58107 16.872 256.48 ± .57 1. 33 1 .79 D 1050 18.2 97.3 0.00 0 16.882 256.62 ± .18 1. 22 1 .71 E 1100 30.1 99.0 15276.96 0 16.557 252.01 ± .30 1. 22 1 .69 F 1150 12.7 98.4 233.84 0 16.532 251.66 t .09 1. 18 1 .67 G 1200 8.2 97.4 130.53 0 16.776 255.12 ± .42 1. 27 1 .74 H 1250 11.4 98.6 263.77 0 16.740 254.61 ± .35 1. 24 1 .72 I 1450 10.8 99.4 18.57 0 16.750 254.75 ± .33 1. 24 1 .72 Total gas K/Ca =

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296. 5 ±.5 J = 0.009055 ± 0.50% (intra-package) ± 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.62 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 3 5.937 EALL: 2 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.000E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 t 0.00 Ca-factors: 3637=2. 6E-04±1 .7E-06 3837=3. 2E-05±2.4E-07 3937=6. 7E-04i 3.7E-06 K-factors: 3739=0. OE+00±2.2E- 03 3839=1 .3E-02±2.4E-04 4039=5. 7E-03i4.0E-03

J = 0.009055 ± 0.50% SAMPLE WT = 0.1 020 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE * ** C 40Ar 39Ar 38Ar 37Ar 36Ar in Ha

900 3.717E-12 2.106E-13 *** 1.151E-15 8.419E-16 250. 70 ± .92 950 6.185E-12 3.553E-13 *** 1.422E-15 8.073E-16 254. 54 ± 1.35 1000 1.477E-11 8.294E-13 *** 1.583E-15 2.613E-15 256. 48 ± .57 1050 5.151E-11 2.969E-12 *** *** 4.699E-15 256. 62 ± .18 1100 8.194E-11 4.901E-12 *** *** 2.719E-15 252. 01 ± .30 1150 3.484E-11 2.072E-12 *** 4.609E-15 1.945E-15 251. 66 ± .09 1200 2.296E-11 1.333E-12 *** 5.311E-15 2.022E-15 255. 12 ± .42 1250 3.167E-11 1.864E-12 *** 3.676E-15 1.548E-15 254. 61 ± .35 1450 2.980E-11 1.768E-12 *** 4.951E-14 *** 254. 75 ± .33 TOTAL 2.774E-10 1.630E-11 *** 6.742E-14 1.780E-14 25 3.92 GAS

NO PLATEAU

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 t 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package 35 reproducibility. *** below detection limit

v 06/13/92 v 06/13/92 03:54:58 23 Jan 1993 91-524 #24 RD87

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v 06/13/92 (40/36in = 295.5) v 06/13/92 03:51:51 23 Jan 1993 91-524 #24 RD87

Point A deleted; 8 points regressed out of 9 includes 98.7 % of 39Ar Mean X = .583E-01 Mean Y = .830E-04 Slope = -.406E-01 a+£ .704E-02 36/40 = .245E-02 a+£ .410E-03 39/40 = .604E-01 a+g .413E-03 Fit parameters: SUMS = 3.089 MSWD = .515 40Ar/36Ar = 408.28 a+g 68.4 F = 16.568 a+g .113 AGE = 252.17 a+g 1.99 Ma

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RAW DATA

TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

30902 1050 488146 20979 2071 178499 209 200 BALL - 999 49 12 105 6 30903 1075 2154533 100781 9724 832910 695 200 BALL - 3200 121 10 672 10 30904 1100 1510772 70897 6886 581766 503 200 BALL . 1066 66 14 718 10 30905 1125 241254 10964 1047 88782 113 200 BALL . 94 14 11 121 3 30906 1150 190329 8603 884 69088 122 200 BALL . 44 13 14 40 2 30907 1175 396287 18156 1768 146558 184 200 BALL . 220 18 6 60 3 30908 1200 159483 7091 697 57054 98 200 BALL - 18 12 3 4 3 30909 1250 204505 9402 919 74111 99 200 EALL 78 13 13 75 10

C 0 R R E C T IONS v A _ . ^ ^ EM «JIQAy 7/VL *J / f*JL Ca-derived Cl-der Initial C Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1050 6 252927 118 278 0 291 14 114 0 18 1075 30 1181280 565 1334 0 1359 64 533 1 31 1100 21 825865 398 938 0 950 45 373 0 25 1125 3 126148 62 145 0 145 7 57 0 11 1150 3 98255 48 114 0 113 5 44 0 15 1175 5 208621 102 240 0 240 11 94 0 17 1200 2 81291 40 94 0 93 4 37 0 12 1250 3 105689 53 125 0 121 6 48 0 10

All values in counts, corrected for mass discrimination

38 v 06/13/92 91-521 #91,92,93 RD85 00:07:22 23 Jan 1993

preco.si.on TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 1050 8.5 94.2 .02 28 22 .207 339. 13 1.43 2.11 2.62 B 1075 40.8 97.8 .03 29 21 .155 324. 43 - .60 1.61 2.20 C 1100 28.7 97.4 .03 29 21 .013 322. 44 - .66 1.62 2.20 D 1125 4.4 93.1 .03 29 20 .727 318. 41 - 1.14 1.86 2.37 E 1150 3.5 87.9 .03 26 19 .687 303. 71 - .98 1.71 2.22 F 1175 7.4 93.3 .03 28 20 .604 316. 68 - .73 1.63 2.19 G 1200 2.9 88.5 .03 28 20 .139 310. 12 - 2.07 2.52 2.90 H 1250 3.8 92.6 .03 28 20 .367 313. 34 - 4.29 4.53 4.76 Total gas K/Ca = 0.0

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 J = 0.009313 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 4.2 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.344E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03

J = 0.009313 0.50% SAMPLE WT = 1.0017 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1050 1.312E-11 5.567E-13 4.842E-14 1.163E-11 2.555E-15 339.13 - 1.43 1075 5.790E-11 2.676E-12 2.251E-13 5.428E-11 4.391E-15 324.43 - .60 1100 4.060E-11 1.882E-12 1.596E-13 3.793E-11 3.536E-15 322.44 .66 1125 6.483E-12 2.912E-13 2.439E-14 5.792E-12 1.518E-15 318.41 - 1.14 1150 5.115E-12 2.285E-13 2.099E-14 4.510E-12 2.087E-15 303.71 - .98 1175 1.065E-11 4.821E-13 4.129E-14 9.571E-12 2.421E-15 316.68 - .73 1200 4.286E-12 1.883E-13 1.645E-14 3.728E-12 1.670E-15 310.12 - 2.07 1250 5.496E-12 2.497E-13 2.150E-14 4.845E-12 1.384E-15 313.34 - 4.29 TOTAL 1.436E-10 6.554E-12 5.577E-13 1.323E-10 1.956E-14 322.73 GAS

69.5% of gas on plateau, steps 1075 through 1100 PLATEAU AGE = 323.52 + 1.66

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. 39 *** below detection limit

v 06/13/92 "~~ v 06/13/92 00:08:04 23 Jan 1993 91-521 #91,92,93 RD85

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v 06/13/92 (40/36in = 295.5) X v 06/13/92 00:14:33 23 Jan 1993 1-521 #91,92,93 RD85

Points DEFGH deleted; 3 points regressed out of 8 includes 78 % of 39Ar Mean X = .448E-01 Mean Y = .125E-03 Slope = -.296E-01 a+£ .443E-02 36/40 = .145E-02 a+g .199E-03 39/40 = .490E-01 a+£ .691E-03 Fit parameters: SUMS = .554 MSWD = .554 40Ar/36Ar = 689.77 a+g 94.48 F = 20.401 a+g .288 AGE = 313.82 a+£ 4.31 Ma

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RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

30881 1050 377685 15800 2739 48215 78 200 EALL . 292 11 9 65 5 30882 1100 1606668 69260 12387 181696 161 200 ESPLIT . 756 27 12 234 3 30883 1125 3010216 129500 22730 327550 270 200 EALL . 4916 66 26 624 5 30884 1140 1040101 45202 7693 107934 92 200 EALL . 396 15 14 122 10 30885 1160 290199 12839 2132 31297 35 200 EALL . 50 9 10 27 5 30886 1175 250691 11225 1923 28160 45 200 EALL . 97 9 8 30 2 30887 1200 341239 15194 2600 38108 40 200 EALL 160 13 14 24 3

CORRECTIONS

39Ar 37Ar K-derived- Ca-derived Cl-der Initial Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1050 5 66693 89 211 0 78 4 30 0 9 1100 20 251606 392 925 0 292 14 115 1 9 1125 37 454006 733 1730 0 527 25 207 2 12 1140 13 149742 256 604 0 174 8 68 1 4 1160 4 43460 73 172 0 50 2 20 0 3 1175 3 39139 64 150 0 45 2 18 0 5 1200 4 53015 86 203 0 61 3 24 0 3

All values in counts, corrected for mass discrimination

42 v 06/13/92 91-523 #120,121 RD85 00:21:31 23 Jan 1993

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 1050 3.4 96.3 .07 15 23 .100 346. 04 1.36 2.09 2.61 B 1100 49.9 99.2 .08 15 23 .067 345. 59 .22 1.59 2.24 C 1125 28.3 99.4 .09 15 23 .165 346. 92 .55 1.68 2.30 D 1140 9.9 99.3 .09 15 22 .914 343. 50 .87 1.80 2.38 E 1160 2.8 98.5 .09 16 22 .319 335. 37 1.59 2.21 2.69 F 1175 2.4 96.8 .09 15 21 .672 326. 47 .59 1.61 2.20 G 1200 3.3 98.6 .09 15 22 .205 333. 79 .92 1.78 2.35 Total gas K/Ca = .1

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 -.5 J = 0.009154 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200; Manifold factors- ALL: 1 SPLIT 1: 4.2 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.344E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.0E-03

======J == 0.009154 0.50% SAMPLE WT = 0.6662 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1050 1.015E-11 4.231E-13 6.823E-14 3.097E-12 1.272E-15 346.04 1.36 1100 1.425E-10 6.125E-12 1.018E-12 3.853E-11 4.081E-15 345.59 .22 1125 8.089E-11 3.471E-12 5.652E-13 2.106E-11 1.679E-15 346.92 .55 1140 2.795E-11 1.212E-12 1.908E-13 6.944E-12 *** 343.50 .87 1160 7.799E-12 3.441E-13 5.280E-14 2.015E-12 *** 335.37 1.59 1175 6.737E-12 3.008E-13 4.784E-14 1.814E-12 *** 326.47 .59 1200 9.170E-12 4.072E-13 6.456E-14 2.456E-12 *** 333.79 .92 TOTAL 2.852E-10 1.228E-11 2.008E-12 7.592E-11 9.226E-15 344.63 GAS

81.6% of gas on plateau, steps 1050 through 1125 PLATEAU AGE 345.83 + 1.76

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit 43

v 06/13/92 / 06/13/92 00:24:24 23 Jan 1993 91-523 #120,121 RD85

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v 06/13/92 (40/36in = 295.5) X v 06/13/92 00:32:17 23 Jan 1993 91-523 #120,121 RD85

Points EFG deleted; 4 points regressed out of 7 includes 91.4 % of 39Ar Mean X = . 427E-01 Mean Y = 535E-04 Slope = -.705E-01 a+g .119E-01 36/40 = .306E-02 a+£ .506E-03 39/40 = .434E-01 a+£ .168E-03 Fit parameters: SUMS = 2.117 MSWD = 1.058 40Ar/36Ar = 326.59 a+£ 53.93 F = 23.034 a+g .089 AGE = 345.14 a+£ 1.99 Ma

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RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34853 450 3152946 161371 5509 12 110 40 BALL 567 78 9 6

CORRECTIONS

TEMP 39Ar 37Ar K-derived Ca-derived Cl-der Initial C Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

450 216 445 919 2167 20

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 450 100.0 99.0 183.73 116 19.291 290.43 17 1.36 1.91 Total gas K/Ca = 183.7

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 -.5 J - 0.009055 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 2.26 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 35.937 BALL: 2.1167 ESPLIT 1: 7.77 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.0E-03

J = 0.009055 0.50% SAMPLE WT = 0.0520 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* ** C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

450 2.224E-10 1.141E-11 2.379E-13 3.230E-14 7.712E-15 290.43 .17

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** l-s4^na precision estimates for plateaux are for intra-irradiation package reproduc ib i1ity. *** below detection limit

v 06/13/92 v 06/13/92 91522 #22 RD87 02:33:45 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

32772 900 180332 10583 77 0 12 200 EALL 41 11 12 10 2 32773 950 463481 27555 377 0 28 200 EALL 925 33 3 5 7 32774 1000 1046930 61678 791 0 52 200 EALL 867 67 14 16 5 32775 1050 2831884 167545 2121 0 50 200 EALL 1906 70 21 18 7 32776 1100 1658661 99695 1263 0 25 200 EALL 2612 155 10 16 6 32777 1150 641014 38414 492 0 31 200 EALL 227 20 12 19 2 32778 1200 511962 30601 399 7 26 200 EALL 627 14 19 9 6 32779 1250 529934 31652 402 0 10 200 EALL 355 12 12 12 3 32780 1450 1666771 99135 1225 356 22 200 EALL 2650 148 11 8 4

C/ "l/^T>T>T*'-l«O R R E C T1«'*- ]EONS --

TMTMQ 3 Q AT- 37Ar K-d<=r-iv<=H iCtnir «J ^*V&. Ca-derived Cl-der Initial |c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

900 3 0 60 142 0 000-0 2 950 7 0 157 370 0 0000 5 1000 16 0 351 827 0 000-0 10 1050 45 0 953 2248 0 000-0 9 1100 27 0 567 1337 0 000-0 5 1150 10 0 218 515 0 000-0 6 1200 8 8 174 411 0 000-0 5 1250 8 0 180 425 0 000-0 2 1450 26 406 564 1330 0 100-0 4

All values in counts, corrected for mass discrimination v 06/13/92 91522 #22 RD87 02:33:47 23 Jan 1993

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 900 1.9 98.1 0 .00 0 16.685 253. 82 .66 1.36 1.81 B 950 4.9 98.2 0 .00 5188 16.500 251. 20 1.19 1.67 2.04 C 1000 10.9 98.5 0 .00 0 16.700 254. 03 - .39 1.25 1.72 D 1050 29.6 99.5 0 .00 0 16.789 255. 30 - .24 1.22 1.70 E 1100 17.6 99.6 0 .00 0 16.538 251. 75 .45 1.26 1.72 F 1150 6.8 98.5 0 .00 0 16.421 250. 08 .22 1.19 1.67 G 1200 5.4 98.5 1096 .83 0 16.451 250. 51 .94 1.50 1.91 H 1250 5.6 99.4 0 .00 0 16.624 252. 97 « .38 1.24 1.72 I 1450 17.5 99.6 67 .56 0 16.724 254. 38 .41 1.26 1.73 Total gas K/Ca = 71. 0

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 «.5 J = 0.009055 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.515 SPLIT 2: 10.89 SPLIT 3: 35.937 BALL: 2 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.344E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.0E-03

J = 0.009055 0.50% SAMPLE WT = 0.1016 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

900 4.846E-12 2.848E-13 ** * * * * * * * 253.82 .66 950 1.245E-11 7.415E-13 * * * ** * * * * 251.20 1.19 1000 2.813E-11 1.660E-12 *** * * * 1.404E-15 254.03 .39 1050 7.610E-11 4.509E-12 ** * ** * 1.360E-15 255.30 .24 1100 4.457E-11 2.683E-12 *** * * * *** 251.75 .45 1150 1.722E-11 1.034E-12 ** * ** * *** 250.08 .22 1200 1.376E-11 8.235E-13 *** *** * * * 250.51 .94 1250 1.424E-11 8.518E-13 * * * * * * *** 252.97 .38 1450 4.479E-11 2.668E-12 ** * 2.053E-14 * * * 254.38 .41 TOTAL 2.561E-10 1.525E-11 * * * 2.092E-14 6.916E-15 253.41 GAS

NO PLATEAU

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sijOma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit

v 06/13/92 v 06/13/92 02:35:16 23 Jan 1993 91522 #22 RD87 v 06/13/92 02:42:15 23 Jan 1993 91-522 #22 RD87

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v 06/13/92 (40/36in = 295.5) v 06/13/92 02:56:32 22 Jan 1993 91-522 #22 RD87

Points EFGHI deleted; 4 points regressed out of 9 includes 47.2 % of 39Ar .248E-01 Mean X = .590E-01 Mean Y = , 562E-04 Slope = -.316E-01 36/40 = .192E-02 a+g .147E-02 39/40 = .608E-01 a+g .145E-02 Fit parameters: SUMS = 3.894 MSWD = 1.947 5.72 Ma 40Ar/36Ar = 520.87 a+g 397.56 F = 16.459 a+g .394 AGE = 250.62

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mCO

I LU OJ

.01 .02 .03 .04 .05 .OR 50 39 W/0 POINTS EFGHI / 06/13/92 03:41:53 23 Jan 1993 91-530 #26 RD87

J = 0.009055 0.50% SAMPLE WT = 0.1008 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1150 4.708E-12 2.816E-13 *** *** * * * 248.02 1.80 1200 6.507E-12 3.875E-13 *** * * * * * * 251.98 - 3.08 1250 8.167E-12 4.883E-13 * * * * ** *** 252.57 - 2.19 1450 2.802E-11 1.684E-12 ** * 3.765E-14 *** 251.67 - .36 TOTAL 4.740E-11 2.842E-12 * * * 3.886E-14 1.514E-15 251.51 GAS

90.1% of gas on plateau, steps 1200 through 1450 PLATEAU AGE = 251.70 + 1.31

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproduc ib i1ity. *** below detection limit v 06/13/92

51 v 06/13/92 91-530 #26 RD87 03:41:50 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

32757 1150 175190 10465 74 3 16 200 EALL 118 20 10 11 4 32758 1200 242162 14399 83 17 12 200 EALL 144 7 12 2 11 32759 1250 303927 18147 109 1 8 200 EALL 211 21 14 12 9 32760 1450 1042624 62593 789 661 22 200 EALL 1176 81 2 16 4

CORRECTIONS

39Ar 37Ar K-derived Ca-derived Cl-der Initial Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1150 3 3 60 140 0 0 0 0 -0 3 1200 4 19 82 193 0 0 0 0 -0 2 1250 5 1 103 243 0 0 0 0 -0 1 1450 16 737 356 840 0 1 0 0 -0 4

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 1150 9.9 97.4 864 .30 0 16. 277 248. 02 1.80 2.15 2.44 B 1200 13.6 98.6 207 .21 0 16. 555 251. 98 - 3.08 3.30 3.50 C 1250 17.2 99.2 4256 .60 0 16. 596 252. 57 2.19 2.49 2.76 D 1450 59.3 99.4 23 .26 0 16. 533 251. 67 .36 1.23 1.70 Total gas K/Ca = 859. 1

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 -.5 J = 0.009055 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.51 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.344E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03

52 O Apparent Age (Ma) K/Ca 01 ro ro CxJ CO CTI CD Lx) CD en CD CD \ CD CD CD LO CD 11 Illl I I I I III I I I I I III

s: LO CO cz -* LO CO I C~D en CD CO

CO

CO

Lx) Ol

ui u> ru LO LJ1 CD LJ1 v 06/13/92 03:46:08 23 Jan 1993 91-530 #26 RD87 Point A deleted; 3 points regressed out of 4 includes 90.1 % of 39Ar Mean X = .598E-01 Mean Y = .334E-04 Slope = -.487E-01 . 136E+00 36/40 = .294E-02 a+£ .813E-02 39/40 = .605E-01 a+£ .205E-02 Fit parameters: SUMS = .021 MSWD = .021 40Ar/36Ar = 339.82 a+£ 938.94 F = 16.536 a+ .559 AGE = 251.71 8.04 Ma

91-530

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.01 .02 .03 .04 .05 .06 54 39 ArAr W/0 POINTS A v 06/13/92 91-531 #34,35 HBL CONC RD87 08:48:25 28 Aug 1992

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD regression CURRENT OPTION

32692 1200 390873 19317 632 105482 93 200 EALL * 292 35 13 94 7 32693 1225 489937 24420 963 131906 109 200 EALL * 338 11 10 84 6 32694 1250 306726 15422 503 81556 76 200 EALL ± 264 13 10 26 5 32695 1350 728835 37168 1467 194810 146 20 0 EALL ± 839 17 7 261 6 32696 1450 686929 34701 1362 178182 137 20 0 EALL * 1136 55 14 247 7

C 0 R R E C T I 0 N S

TEMP 39Ar 37Ar tltll 1 VCU ----Ca-derived---- Cl- der Initial °C Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36 Ar 38Ar

1200 5 110280 109 257 0 146 7 57 0 7 1225 6 138031 138 325 0 182 9 72 0 7 1250 4 85421 87 205 0 113 5 44 0 6 1350 9 204233 210 495 0 270 13 106 0 8 1450 9 186971 196 462 0 247 12 97 0 8

All values in counts, corrected for mass discrimination1

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/Cl (Ma) sample package package

A 1200 14.7 97.2 .05 123 19. 784 298.44 ± 1.59 2 11 2.52 B 1225 18.6 97.7 .05 92 19. 711 297.41 ± 1.01 1 .71 2.19 C 1250 11.8 96.9 .05 124 19. 378 292.77 ± 1.27 1 .86 2.30 0 1350 28.4 98.3 .05 92 19. 386 292.89 ± .76 1 .55 2.06 E 1450 26.5 98.2 .05 93 19. 546 295.12 ± .96 1 .67 2.16 Total gas K/Ca = 0.0

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 297.2 ±.5 J = 0.009093 ± 0.50X (intra-package) ± 0.50X (inter-package) Trap current factors- 40: 5.66 100: 2.62 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.000E-17 X Reproducibility = .25 Detection limit) = 40 counts Data reduced.assuming initial 40/36 = 295.50 ± 0.00 I Ca-factors: 3637=2.6E-04±1.7E-06 3837=3.2E-05±2.4E-07 3937=6.7E-04±3.7E-06 55 K-factors: 3739=0.OE+00±2.2E-03 3839=1-3E-02±2.4E-04 4039=5.7E-03±'4.0E-03 v 06/13/92 08:48:38 28 Aug 1992 91-531 #34,35 HBL CONC RD87

J = 0.009093 ± 0.50% SAMPLE WT = 0.4553 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* ** C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma i

1200 7.815E-12 3.841E-13 7 .529E-15 4 .334E-12 *** 298.44 ± 1.59 1225 9.796E-12 4.856E-13 1 .279E-14 5 .422E-12 *** 297.41 ± 1.01 1250 6.133E-12 3.067E-13 5 .993E-15 3 .354E-12 *** 292 J77 ± 1.27 1350 1.457E-11 7.392E-13 1 .942E-14 8 .015E-12 8.189E-16 292. '89 ± .76 1450 1.373E-11 6.903E-13 1.799E-14 7 .335E-12 8.225E-16 295.12 ± .96 TOTAL 5.205E-11 2.606E-12 6.372E-14 2 .846E-11 3.776E-15 295. 13 GAS

66.6% of gas on plateau, steps 1250 through 1450 PLATEAU AGE = 93.57 + 1.38

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 ± 0 ** 1-sigma precision estimates are for intra-sample reproducibiIity. ** 1-sigma precision estimates for plateaux are for intra-irradistion package reproducibiIity. *** below detection limit v 06/13/92

56 O Apparent Age (Ma) K/Ca Ol ro ro CO CO UJ CD en CD en \ CD CD ruLD

to UI

HI CD CO CD i-^ CO 3D I 1^ CJ1 CD CO

3D

D CD

CO nn CD CD

DD

U) 01 M- D II 01 ro ID ui ui CD X v 06/13/92 04:04:58 23 Jan 1993 91-531 #34,35 RD87

Points AB deleted; 3 points regressed out of 5 includes 66.6 % of 39Ar Mean X = .503E-01 Mean Y = .751E-04 Slope = -.630E-01 a+£ .548E-01 36/40 = .324E-02 a+£ .276E-02 39/40 = .515E-01 a+£ .108E-02 Fit parameters: SUMS = .571 MSWD = .571 40Ar/36Ar = 308.33 a+£ 262.15 F = 19.423 a+g .409 AGE = 293.4 a+$ 5.86 Ma

91-531

IT) I

OD

LO I

.009 .018 .027 .036 .045 054 58 39 ArAr W/0 POINTS AB v 06/13/92 91-529 #20 RD87 06:27:52 23 Jan 1993

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 750 2.3 93.6 2367 .85 0 16.861 256 .32 - 1.11 1.63 2.03 B 900 49.1 98.7 195 .46 0 16.642 253 .22 - .19 1.20 1.69 C 950 15.1 99.7 0 .00 0 16.492 251 .09 - .13 1.18 1.67 D 1000 5.7 98.6 0 .00 0 16.407 249 .89 - .47 1.26 1.72 E 1050 5.0 98.9 0 .00 0 16.467 250 .73 - .80 1.42 1.84 F 1100 6.4 98.8 0 .00 0 16.395 249 .70 .36 1.22 1.69 G 1150 11.9 99.4 0 .00 0 16.452 250 .52 - .33 1.22 1.69 H 1200 4.4 99.2 0 .00 8337 16.486 251 .01 - .77 1.41 1.83 Total gas K/Ca = 150. 9

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 -.5 J = 0.009055 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 2.26 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.1167 ESPLIT 1: 7.77 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.0E-03

J = 0.009055 . 0.50% SAMPLE WT = 0.1011 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

750 1.115E-11 6.189E-13 ** * ** * 2.404E-15 256.32 1.11 900 2.207E-10 1.309E-11 *** 3.483E-14 9.616E-15 253.22 .19 950 6.648E-11 4.020E-12 *** *** *** 251.09 .13 1000 2.544E-11 1.529E-12 *** * * * *** 249.89 .47 1050 2.233E-11 1.341E-12 *** * ** ** * 250.73 .80 1100 2.838E-11 1.710E-12 *** *** *** 249.70 .36 1150 5.265E-11 3.180E-12 * * * * * * ** * 250.52 .33 1200 1.947E-11 1.171E-12 *** *** ** * 251.01 - .77 TOTAL 4.466E-10 2.666E-11 *** 3.497E-14 1.748E-14 252.01 GAS

NO PLATEAU

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigtna precision estimates are for intra-sample reproducibility. ** 1-sigtna precision estimates for plateaux are for intra-irradiation package reproducibility. 59 *** below detection limit

v 06/13/92 O Apparent Age (Ma) K/Ca on O no ro CO un CJl UJ O x. CD CTi ruID

LO UJ CO CO I C~D cn CDPO -< UD 10

CO

LO on

ro ID m 1 LJl v 06/13/92 06:32:19 23 Jan 1993 91-529 #20 RD87 Point deleted; 8 points regressed out of 8 Mean X = .593E-01 Mean Y = .647E-04 Slope = -.397E-01 a+g .347E-02 36/40 = .242E-02 a+g .206E-03 39/40 = .609E-01 a+g .212E-03 Fit parameters: SUMS = 3.476 MSWD = .579 40Ar/36Ar = 413.97 a+g 35.3 F = 16.422 a+g .057 AGE = 250.09 a+g 1.42 Ma

91-529

CO m

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,01 .02 .03 .04 .05 .Ofel 39 v 06/13/92 91-529 #10 RD87 06:33:39 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34849 450 1794937 95139 1688 0 41 40 BALL 728 37 784

CORRECTIONS

TEMP 39Ar 37Ar K-derived Ca-derived Cl-der Initial |c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

450 127 0 542 1278 0000

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 450 100.0 99.3 0.00 548 18.692 280.43 - .20 1.32 1.85 Total gas K/Ca = 0.0

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 -.5 J = 0.008998 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 2.26 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.1167 ESPLIT 1: 7.77 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03

J = 0.008998 0.50% SAMPLE WT = 0.0508 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

450 1.266E-10 6.728E-12 2.972E-14 *** 2.899E-15 280.43 .20

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-s^qma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reprodu cibility. *** below detection limit

v 06/13/92 v 06/13/92 91-528 #16 RD87 06:38:28 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34852 550 2677857 157414 4461 10 126 40 EALL 2962 96 11 11 6

CORRECTIONS

TEMP 39Ar 37Ar K-derived Ca-derived Cl-der Initial |c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

550 211 374 896 2114 0 0 0 0 1 24

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/Cl (Ma) sample package package

A 550 100.0 98.6 212.86 161 16.733 254.51 .32 1.23 1.71 Total gas K/Ca = 212.9

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 «.5 J = 0.009055 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 2.26 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 35.937 BALL: 2.1167 ESPLIT 1: 7.77 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.0E-03

J = 0.009055 0.50% SAMPLE WT = 0.0526 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* ** C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

550 1.889E-10 1.113E-11 1.678E-13 2.719E-14 8.885E-15 254.51 - .32

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. 63 ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit v 06/13/92 ~~ i ~~~ v 06/13/92 91-533 #41,42 RD87 04:09:07 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

32710 1225 240511 12697 682 116478 87 200 EALL 282 26 10 44 5 32711 1250 215446 11696 662 108246 79 200 EALL 179 14 8 47 7 32712 1350 530469 29519 1957 274638 194 200 EALL 304 20 8 360 6 32713 1450 80224 4334 254 40147 42 200 EALL 122 7 11 80 6

C 0 R R E C T IONS

TEMP 39Ar 37Ar K-derivr'-j Ca-derived Cl-der Initial |c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1225 3 123998 71 168 0 162 8 64 0 4 1250 3 115339 66 155 0 151 7 59 0 4 1350 7 292899 166 391 0 383 18 150 0 8 1450 1 42855 24 57 0 56 3 22 0 4

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 1225 21.8 97.1 .03 59 18. 608 280 .19 1.60 2.06 2.44 B 1250 20.1 97.2 .03 55 18. 117 273 .34 2.48 2.79 3.06 C 1350 50.7 97.5 .03 45 17. 727 267 ,86 .83 1.50 1.95 D 1450 7.4 92.7 .03 52 17. 362 262 .73 5.76 5.89 6.02 Total gas K/Ca = 0.0

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 J = 0.009030 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.51 SPLIT 2 10.89 SPLIT 3: 35.937 EALL: 2 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.344E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0. OE-»-00«2 . 2E-03 3839 = 1. 3E-02«2. 4E-04 4039=5.7E-03-4.0E-03

64 v 06/13/92 04:09:11 23 Jan 1993 91-533 #41,42 RD87

J = 0 .009030 0 .50% SAMPLE WT = 0.6030 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1225 6. 463E-12 3. 373E-13 1. 374E-14 6.480E-12 *** 280 .19 1.60 1250 5. 789E-12 3. 107E-13 1. 357E-14 6.025E-12 *** 273 .34 2.48 1350 1. 425E-11 7. 841E-13 4. 193E-14 1.529E-11 1.204E-15 267 .86 - .83 1450 2. 156E-12 1. 151E-13 5. 317E-15 2.237E-12 *** 262 .73 5.76 TOTAL 2. 866E-11 1. 547E-12 7. 456E-14 3.004E-11 2.910E-15 271.28 GAS

58.1% of gas on plateau, steps 1350 through 1450 PLATEAU AGE = 267.76 + 1.39

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit v 06/13/92

65 v 06/13/92 04:09:52 23 Jan 1993 91-533 #41,42 RD87

.1

ro

.01

350 91-533 HORNBLENDE CONCENTRATE

cu CD 300

OJ c_ CO Q_ Q_

250

200 I I 66 0 39 An, RELEASED (%) 100

v 06/13/92 (40/36in = 295.5) v 06/13/92 04:15:55 23 Jan 1993 91-533 #41,42 RD87

Point A deleted; 3 points regressed out of 4 includes 78.2 % of 39Ar Mean X = .542E-01 Mean Y = .105E-03 Slope = -.322E-01 a+ .374E-01 36/40 = .185E-02 a+£ .203E-02 39/40 = .575E-01 a+g .411E-02 Fit parameters: SUMS = 2.502 MSWD = 2.502 40Ar/36Ar = 539.74 a+g 590.75 F = 17.403 a+£ 1.246 AGE = 263.31 a+g 17.59 M a

91-533

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.01 .02 .03 .04 .05 67 .06 39 AnAr W/0 POINTS A v 06/13/92 5-328 #40,41,42 HBL RD59 00:08:06 9 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

19933 : 850 295265 12194 211 1384 132 200 ALL 232 33 14 30 3 19934 : 950 301334 14673 268 3782 128 200 ALL 358 30 15 10 13 19935 : 1000 460394 22437 456 14395 184 200 ALL 257 32 23 21 17 19936 : 1050 1920587 100077 2215 71153 339 200 ALL 912 50 17 36 12 19937 : 1100 1691046 91817 1999 42627 169 100 ALL 679 30 8 27 12 19938 : 1125 3015702 168809 3706 74785 244 100 ALL 1641 38 12 18 7 19939 : 1150 3743193 213793 4653 93383 268 100 ALL 924 41 5 64 12 19940 : 1175 2794229 159890 3513 69817 202 100 ALL 1206 80 10 59 17 19941 : 1200 2125039 121475 2685 53287 166 100 ALL 746 58 24 31 23 19942 : 1225 4476099 252658 5577 112896 416 200 ALL 2427 164 18 50 7 19943 : 1250 3866618 216175 4784 95979 310 200 ALL 749 130 8 49 25 19944 : 1350 1637779 91285 1971 39812 119 100 ALL 1384 86 16 37 21 19945 : 1450 554246 30413 733 13566 75 200 ALL 43 21 7 33 11

38Ar errors assigned from experience, rest calculated from regression statistics

CORRECT IONS

TEMP 39Ar 37Ar K-derived v^o.Pa --derived Cl-der Initial C Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

850 10 12287 69 164 0 9 0 4 0 24 950 12 33606 83 197 0 25 1 10 0 22 1000 18 127980 127 300 0 96 5 38 0 27 1050 82 633319 567 1337 0 475 22 186 0 29 1100 75 379673 521 1229 0 285 13 112 0 11 1125 138 666714 958 2259 0 500 24 196 0 9 1150 175 833095 1213 2861 0 625 29 245 0 4 1175 131 623708 907 2140 0 468 22 184 0 4 1200 99 476369 689 1626 0 357 17 140 0 5 1225 207 1010168 1433 3381 0 758 36 297 0 22 1250 177 859391 1226 2893 0 645 30 253 0 11 1350 68 75 356720 518 1222 0 268 13 105 0 3 1450 25 121635 173 407 0 91 4 36 0 7

All values in counts, corrected for mass discrimination v 06/13/92 i-328 #40,41,42 HBL RD59 00:08:08 9 Jan 1993

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 850 .3 87.1 .46 415 21. 062 321. 84 .97 1.77 2.31 B 950 .4 88.4 .20 383 18. 147 280. 57 3.83 4.04 4.25 C 1000 .6 90.6 .08 301 18. 628 287. 44 3.24 3.51 3.75 D 1050 2.5 97.6 .07 272 18. 789 289. 74 .53 1.45 1.97 E 1100 9.1 99.0 .11 288 18. 253 282. 09 .57 1.43 1.94 F 1125 16.7 99.5 .12 284 17. 798 275. 56 .23 1.30 1.83 G 1150 21.2 99.8 .12 291 17. 492 271. 17 .26 1.29 1.80 H 1175 15.8 99.8 .12 284 17. 457 270. 67 .47 1.35 1.84 I 1200 12.0 99.6 .12 279 17. 446 270. 50 .81 1.50 1.95 J 1225 6.3 99.2 .12 279 17. 593 272. 62 .18 1.28 1.80 K 1250 5.4 99.6 .12 278 17. 826 275. 96 - .49 1.38 1.88 L 1350 9.0 99.7 .12 297 17. 913 277 . 21 - 1.02 1.64 2.09 M 1450 .8 97.9 .12 223 17. 855 276. 38 - 1.58 2.03 2.41 Total gas K/Ca = .1

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 «.5 J = 0.009273 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 8.6 100: 4 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.515 SPLIT 2: 12.355 SPLIT 3: 35.937 BALL: 2 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 6.460E-18 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5. 7E-03-4.0E-03

69 v 06/13/92 00:08:12 9 Jan 1993 88-328 #40,41,42 HBL RD59

J := 0.009273 0.50% SAMPLE WT = 0.9995 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* ** C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

850 1.907E-12 7.885E-14 4 .593E-16 8. 854E-14 8 .333E-16 321. 84 .97 950 1.946E-12 9.478E-14 5 .985E-16 2. 421E-13 7 .649E-16 280. 57 3.83 1000 2.973E-12 1.446E-13 1 .164E-15 9. 221E-13 9 .490E-16 287. 44 3.24 1050 1.240E-11 6.445E-13 5 .738E-15 4. 562E-12 9 .941E-16 289. 74 .53 1100 4.368E-11 2.369E-12 1 .993E-14 1. 094E-11 1 .485E-15 282. 09 .57 1125 7.790E-11 4.356E-12 3 .717E-14 1. 921E-11 1 .241E-15 275. 56 .23 1150 9.669E-11 5.517E-12 4 .585E-14 2. 400E-11 *** 271. 17 .26 1175 7.218E-11 4.126E-12 3 .516E-14 1. 797E-11 *** 270. 67 .47 1200 5.489E-11 3.135E-12 2 .718E-14 1. 372E-11 *** 270. 50 .81 1225 2.891E-11 1.630E-12 1 .416E-14 7. 273E-12 7 .758E-16 272. 62 .18 1250 2.497E-11 1.395E-12 1 .215E-14 6. 187E-12 3 .709E-16 275. 96 .49 1350 4.231E-11 2.356E-12 1 .919E-14 1. 027E-11 *** 277. 21 1.02 1450 3.579E-12 1.962E-13 2 .132E-15 8. 756E-13 *** 276. 38 1.58 TOTAL 4.643E-10 2.604E-11 2 .209E-13 1. 163E-10 9 .816E-15 274.42 GAS

NO PLATEAU

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit v 06/13/92

70 v 06/13/92 00:09:02 9 Jan 1993 88-328 #40,41,42 HBL RD59

no .1 LT

.01

350

CTD 88-328

CD HORNBLENDE CD 300

CD C_ h no d. d. 250

200 39 0 Ai\ RELEASED (35) ! 100

v 06/13/92 (40/36in = 295.5) v 06/13/92 00:23:57 9 Jan 1993 88-328 #40,41,42 HBL RD59 Points AB deleted; 11 points regressed out of 13 includes 99.3 % of 39Ar Mean X = .549E-01 Mean Y = .557E-04 Slope = -.323E-01 a+£ .714E-02 36/40 = .183E-02 a+£ .393E-03 39/40 = .567E-01 a+£ . 722E-03 Fit parameters: SUMS = 3.85 MSWD = .428 40Ar/36Ar = 546.19 a+£ 117.19 F = 17.65 a+£ .225 AGE = 273.43 a+ 3.47 Ma

-328

OJ

CO OJ CD C_ §

to m

CD CD

.01 ,02 .03 .04 .05 .06 72 39 ArAr W/0 POINTS AB v 06/13/92 i-330 #43,44,45 HBL RD59 05:18:17 8 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

19238 : 750 370714 15277 1380 11564 274 200 SPLIT 1 233 40 20 23 27 19239 : 850 234276 10035 392 4061 238 200 ALL 54 10 22 6 15 19240 : 950 609474 31059 1976 34133 258 200 ALL 226 26 13 27 13 19241 : 1000 3260844 180375 14122 227618 522 200 ALL 2586 144 32 203 15 19244 : 1050 638525 35510 2820 43371 75 200 SPLIT 2 106 13 24 29 20 19246 : 1075 3514967 196187 15677 237405 311 200 SPLIT 1 1738 107 17 180 17 19248 : 1100 1436669 81063 6442 97516 75 100 SPLIT 1 839 67 10 83 7 19249 : 1125 4653988 263486 21237 315180 326 100 ALL 116 267 36 49 12 19252 : 1150 2873079 162607 13135 195469 195 100 ALL 939 63 14 26 4 19253 : 1175 1569681 88047 7126 106135 134 100 ALL 590 16 11 42 13 19254 : 1200 2929691 162000 13173 195459 296 200 ALL 2334 132 9 153 19 19255 : 1250 4321317 237711 19341 284059 352 200 ALL 2301 125 26 166 8 19256 : 1350 978371 53086 4229 62899 114 200 ALL 390 21 40 11 9

38Ar errors assigned from experience, rest calculated from regression statistics

C 0 R I1 E C T IONS

TEMP 39Ar 37Ar red Ca-derived Cl-der Initial |c Decay Decay 40Ar 38Ar 37Ar 39Ar 38 Ar 36Ar 36Ar 38Ar

750 6 25047 87 205 0 25 1 10 0 50 850 4 8803 57 135 0 9 0 3 0 44 950 12 74065 176 416 0 73 3 29 0 43 1000 71 499424 1023 2413 0 491 23 192 1 62 1050 14 95333 201 475 0 94 4 37 0 7 1075 78 522460 1113 2625 0 513 24 201 1 20 1100 32 214861 460 1085 0 211 10 83 1 -1 1125 105 695281 1495 3526 0 682 32 267 2 11 1150 65 431847 922 2176 0 423 20 166 1 5 1175 35 234692 499 1178 0 230 11 90 1 8 1200 65 432728 919 2168 0 424 20 166 1 24 1250 95 629444 1348 3181 0 616 29 242 2 21 1350 21 139502 301 710 0 137 6 54 0 11 73 All values in counts, corrected for mass discrimination v 06/13/92 $-330 #43,44,45 HBL RD59 05:18:19 Jan 1993

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 750 1.1 78.9 .22 30 19. 144 293 .67 7.34 7.46 7.59 B 850 .2 70.3 .40 80 16. 396 254 .35 6.31 6.43 6.54 C 950 .6 88.9 .15 47 17. 451 269 .54 1.82 2.22 2.55 D 1000 3.6 97.0 .13 37 17. 558 271 .07 .41 1.33 1.83 E 1050 8.7 98.2 .13 36 17. 678 272 .79 2.42 2.73 3.01 F 1075 13.6 99.1 .13 36 17. 771 274 .12 .39 1.33 1.84 G 1100 22.6 100.0 .13 37 17. 770 274 .11 .37 1.33 1.84 H 1125 20.9 99.6 .14 36 17. 617 271 .92 - .19 1.28 1.80 I 1150 12.9 99.7 .13 36 17. 635 272 .18 - .13 1.27 1.80 J 1175 7.0 99.2 .13 36 17. 699 273 .10 .64 1.42 1.91 K 1200 3.2 98.7 .13 35 17. 867 275 .50 .54 1.39 1.89 L 1250 4.7 99.2 .13 35 18. 061 278 .27 .20 1.31 1.84 M 1350 1.1 98.2 .14 36 18. 111 278 .99 .71 1.48 1.97 Total gas K/Ca = .1

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 «.5 J = 0.009235 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 8.6 100: 4 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.515 SPLIT 2: 12.355 SPLIT 3: 35.937 EALL: 2 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 6.460E-18 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03 v 06/13/92 05:18:24 8 Jan 1993 88-330 #43,44,45 HBL RD59

J := 0.009235 0.50% SAMPLE WT = 0.9781 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

750 8.416E-12 3.468E-13 2.783E-14 8.334E-13 6.015E-15 293.67 7.34 850 1.513E-12 6.485E-14 1.950E-15 8.331E-14 1.522E-15 254.35 6.31 950 3.936E-12 2.004E-13 1.036E-14 7.007E-13 1.484E-15 269.54 1.82 1000 2.106E-11 1.163E-12 7.604E-14 4.709E-12 2.132E-15 271.07 .41 1050 5.095E-11 2.830E-12 1.878E-13 1.110E-11 ** * 272.79 2.42 1075 7.979E-11 4.449E-12 2.969E-13 1.730E-11 2.481E-15 274.12 .39 1100 1.304E-10 7.353E-12 4.866E-13 2.844E-11 *** 274.11 .37 1125 1.202E-10 6.799E-12 4.580E-13 2.618E-11 1.486E-15 271.92 .19 1150 7.422E-11 4.196E-12 2.834E-13 1.625E-11 *** 272.18 .13 1175 4.055E-11 2.272E-12 1.539E-13 8.829E-12 1.130E-15 273.10 .64 1200 1.892E-11 1.045E-12 7.127E-14 4.068E-12 8.364E-16 275.50 .54 1250 2.791E-11 1.534E-12 1.046E-13 5.916E-12 7.103E-16 278.27 .20 1350 6.318E-12 3.425E-13 2.281E-14 1.311E-12 3.911E-16 278.99 .71 TOTAL 5.842E-10 3.260E-11 2.181E-12 1.257E-10 2.202E-14 273.45 GAS

NO PLATEAU

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit v 06/13/92

75 o Apparent Age (Ma) K/Ca 01 cn ro ro CxJ Lx) en cn \ CD (D CD _LL J '

co CD I (jj CO O CDCXD DO I ^ CxJ ODCxJ ID I CD

DO mCO CD

Lx) 01 M- D II r\j UD Ul LJ1 v 06/13/92 05:58:18 8 Jan 1993 $-330 #43,44,45 HBL RD59

Points ABM deleted; 10 points regressed out of 13 includes 97.7 % of 39Ar Mean X = .553E-01 Mean Y = .729E-04 Slope = -.661E-01 a+g .202E-01 36/40 = .372E-02 a+g .112E-02 39/40 = .564E-01 a+g .610E-03 Fit parameters: SUMS = .731 MSWD = .091 40Ar/36Ar = 268.47 a+g 80.38 F = 17.74 a+g .192 AGE = 273.68 a+g 3.03 Ma

-330

c_ <=>

CD CO

.05 77.06 Ar/lr W/0 POINTS ABM 88-3:1 1 HORNBLEHIE RD'59 #37-39 R H W D H T fl

FILE TEMP 40 fir 3 9 fi r 3 8 fir 3 7 fi r 36fir TRfiP MfihlFOLIi r egress i on C URRIEHT CPTIOH

750 2288133 8102 413 86 139 20t3 filL + 132 18 12 4 6 850 189735 10330 390 106 1155 2013 fiLL + 147 18 14 13 l:. 950 14192'.59 80369 8422 2098 240 2013 fiL L + 694 32 18 9 12 1000 :24724'7 0 201225 21078 5268 389 20(3 fiL L + 1593 56 10 17 12 ~ O/1 £" iT "7 O 1050 ti! 7 " O D O 171053 17663 4434 263 2013 SFLIT 1 + 318 59 11 6 10 1100 27084158 156096 15066 4084 194 1013 SFLIT 1 + 913 30 10 21 1:. 1125 2417735 139240 13175 3679 187 1013 fiLL + 993 32 9 12 8 1150 S386521 195187 18705 5117 287 2013 fiLL + 12:38 19 12 4 8 1175 1734689 99516 9694 2589 165) 2013 fiLL - 913 81 35 15 15)

33 fir = rors as signed from e x p e r i e n c e , r «= s t c a 1 c u 1 at e-d fron regr«; ssi on st at i st i cs

COR R E C T I 0 N S

TEMP 3 9 H t .. 7 fi r K-deri ved---- C a-der i ued---- C 1 -der Initial «C Decay lecay 49flr 38fir 37fir 39flr 38flr 36flr 36fir 3£ fir

750 15 12119 46 109 0 8 0 3 0 35 850 19 14947 59 139 0 10 0 4 0 21 950 145 256013 457 1077 0 201 9 79 4 30 1000 364 743893 1143 2697 0 505 24 198 9 34 1050 399 626773 972 2292 0 426 20 167 7 17 1100 282 578016 887 2092 0 393 18 154 6 6 1125 252 521020 791 1866 0 354 17 139 5 3 1150 353 725119 1108 2615 0 493 23 193 8 16 1175 180 367034 565 1334 0 249 12 98 4 12

fil 1 values in counts, c o r r e c t e d f o r m ass d i s c r i m i n a- ion

78 3 ' 2 8 -' 9 0 pr.>c is ion TEt'F TOT PhD RPP RPP F Rb E fit r a- i rv ', t'- a inter- f "-: 9 Fir ') I E L D K/Ca K/C1 : amp 1 e t:< a>: k aa t f a c k a Q t

R 750 . 6 -c Q . 34 58 21. 407 326. 92 + 3.14 :3. 49 3. 86 -? E 350 32 . 7 . 36 92 15. 153 237. o o + 4. 65 4. 79 4. 92 C 950 5. 8 96. 7 . 14 26 17. 069 265. 28 T . 66 L . 40 1 . 87 D 10C0 14. 5 98. 4 . 14 26 16. 979 263. 99 + . 29 I . 27 1 . 77 E 1050 44. 4 99. 1 . 14 27 17. 064 265. 21 T . 27 I .27 1 . 77 F 1 1C'0 10.1 99 . 6 . 14 29 17. 278 268. 31 + . 32 I . 29 1 . 80 G 1125 2.5 99 . 5 . 14 30 17. 264 268. 1 1 +_ . 27 1.28 1 . 79 H 1 150 14.1 99. 2 . 14 29 17. 218 267. 43 + .20 I .26 1. 77 I 1 175 7.2 98. 9 . 14 29 17. 234 267. 67 + . 69 I . 43 1 . 89 Total 3 as K/Ca = . 1

Precisions are 1 si gin a, measured in Ma. Measured 40/36 at rn = ;?96.!5 J = C. 309281 _+ G . 50^: < i ntra-package) +_ 0.50/: < i nt er-pac k age ) Trap current factors- 40: 8.6 100: 4 200: 1 Manifold factors- fll.L: 1 SPLIT 1: 3.6 SPLIT 2: 12.96 SPLIT :J: 4i5.656 Sensitivity = 6.470E-18 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 +_ 0. 00 Ca-fa.ctors: 3637 =2. 6IZ-044-1. 7E-66 3837 = 3. 2E-05+2 . 4E-07 3937 = 0. 7E--04 + 3. 7 E-06 K-factDrs: 373S=0.0E+00+2.2E-03 3839=1.3E-02+2.4E-04 4039 = !). 7E--03 + 4.CE-03

,1 = 0. 00928 1 + 0 . 50:-: SRMPLE; WT = i. 0011

Initial 8. Po^ ass i urn C h 1 o r i n e Calcium TEMP r ad i ogen i c d«?r i ued d e r i M e d d e r i v e d I n i t a 1 R G E * * * C: 40Rr 39Rr 38Rr 37Rr 36Rr in Ma

750 i 480E -12 5. 25 IE- 14 0 196E- 15 7. 917E- 14 1 . 205E- 15 32o . 92 + 3.49 850 1 . 227E -12 6. 695E-14 1 . 762E- 15 9. 764E- 14 7. 200E- 16 23'7 . 38 + 4 . 7 'r 950 9 m 180E -12 5. 20 IE- 13 4. 775E- 14 1 . 934E- 12 1 . 625E-- 15 265. 28 + 1.40 1000 ^ , 246E -1 1 1. 302E-12 1 . 192E- 13 4. 859E- 12 1 . 186E--15 263. QQ + 1 . 27 1050 6 . 861E -1 1 3. 985E-12 3 . 587E- 13 1 . 474E- 1 1 2. 084E-- 15 265. 21 T 1 . 27 1 100 1 . 577E -1 1 9. IJ91E-13 ( . 564E- 14 3. 398E- 12 * * * 263. 31 + 1 . 29 1 125 3 . 909E -12 2.252E-13 1 . 832E- 14 8. 509E- 13 7 . 014E-- 17 263. 1 1 + 1.28 1 150 2. 190E -1 1 1.263E-12 1 . 043E- 13 4. 737E- 12 5. 630E- 16 26 -7 . 43 + 1 . 26 1 175 1 . 122E -1 1 6. 440E-13 5. 421E- 14 2 . 398E- 12 4. 124E-- 16 26'7 . 67 +_ 1.43

TOTRL 1 . 558E -ie 8.967E-12 7 . 821E- 13 3. 309E- 1 1 7 . 466E- 15 26.5. 07 GRS K/Ca . 1

64.c* of gas or plateau, steps 950 through 1050 PLRTERU RGE 2's4.70 1.38

Note: all gas cuantities are in moles. No blank correct'on. * Rges calculated assuming initial 40Rr/36Rr = 295.5 +_ 0 ** 1-sigma precision estimates are for intra-irradiation pack-ige reprodici- bi1 i ty. *** br-lou detection limit

3/28'96

79 3/28/90

350 88-331 HORNBLENDE PLRTERU RGE = 265 +\- 1 Ma

CD O) CE 300 P C 03

Q. Q. CE 250

200 0 39 100 Rr Released (X 80 K v 3/28/3088-331 HORNBLENDE RD59 +37-39 (40/36ln - 483.3) 'ID iD Q

IS

(T

\ i_ (T IS C£> IS CD

IS iS iS

iS 0 01 02 .03 .04 .05 .06 39Rr/40Rr

9 '-points regressed out of 9 Mean X = .577E-01 Mean Y = .331E-04 Slope = -.353E-01 +_ . .16E--02 36/4E = .207E-22 ^ ,670E-04 39/40 = .586E-01 + .545E-04 Fit parameters: SUM3 = 224.502 MSWD = 32.072 48flr/3SRr = 483.28 + 15.65 F = 17.064 + .016 RGE = 265.22 - 1.25 Ma

81 v 06/13/92 91-543 #37,38,39 RD87 04:18:50 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

32639 1100 349171 17633 2183 37940 59 200 EALL 390 11 4 42 5 32640 1125 1104891 57261 7505 119138 111 200 EALL 1660 97 18 245 7 32641 1150 2517545 131226 15788 272750 218 200 EALL 3403 143 36 370 12 32642 1170 2631691 138576 15096 293843 228 200 EALL 3202 183 24 729 10 32643 1185 2969949 157621 16237 337314 247 200 EALL 3322 149 17 307 3 32644 1200 3545457 187009 18210 392790 264 200 EALL 8183 426 17 808 9 32645 1225 4709789 257116 16390 606593 389 200 EALL 8988 408 24 1429 8 32646 1250 3671588 205364 11258 514115 336 200 EALL 4459 224 8 469 7 32647 1450 2254565 124292 7998 297549 196 200 ESPLIT 2404 106 21 231 8

C: 0 R R E C T I 0 N S

TEMP 39Ar 37Ar rT,v-derived Ca-derived Cl-der Initial |c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1100 4 36939 100 236 0 51 2 20 0 7 1125 14 116103 325 766 0 159 7 62 0 9 1150 31 266054 744 1755 0 364 17 143 1 14 1170 33 286900 786 1854 0 392 18 154 1 14 1185 37 329654 894 2108 0 450 21 177 1 13 1200 44 384233 1060 2502 0 524 25 206 1 11 1225 61 593939 1457 3438 0 810 38 318 1 13 1250 49 503864 1164 2746 0 687 32 269 1 13 1450 30 291947 704 1662 0 398 19 156 0 7

All values in counts, corrected for mass discrimination

82 v 06/13/92 91-543 #37,38,39 RD87 04:18:52 23 Jan 1993

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 1100 1.1 96.7 .12 22 19. 172 287 .34 1.22 1.81 2.25 B 1125 3.7 98.7 .13 20 19. 073 285 .96 .64 1.47 1.98 C 1150 8.4 99.1 .13 23 19. 042 285 .54 .53 1.43 1.94 D 1170 8.9 99.2 .12 25 18. 861 283 .02 .43 1.38 1.91 E 1185 10.1 99.3 .12 27 18. 737 281 .31 .30 1.34 1.87 F 1200 12.0 99.5 .12 29 18. 894 283 .48 .64 1.46 1.97 G 1225 16.5 99.5 .11 48 18. 267 274 .75 .51 1.38 1.88 H 1250 13.1 99.5 .10 58 17. 816 268 .45 .33 1.30 1.80 I 1450 26.3 99.5 .11 47 18. 077 272 .10 .39 1.33 1.83 Total gas K/Ca = .1

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 «.5 J = 0.009006 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.51 SPLIT 2: 10.89 SPLIT 3: 35.937 BALL: 2 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.344E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03

J = 0.009006 0.50% SAMPLE WT = 0.9833 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* ** C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1100 9.383E-12 4.731E-13 5.258E-14 2.018E-12 *** 287.34 1.22 1125 2.969E-11 1.537E-12 1.815E-13 6.339E-12 1.300E-15 285.96 .64 1150 6.765E-11 3.521E-12 3.778E-13 1.452E-11 2.017E-15 285.54 .53 1170 7.072E-11 3.718E-12 3.565E-13 1.565E-11 1.982E-15 283.02 .43 1185 7.981E-11 4.229E-12 3.803E-13 1.797E-11 1.899E-15 281.31 .30 1200 9.527E-11 5.018E-12 4.227E-13 2.094E-11 1.554E-15 283.48 .64 1225 1.266E-10 6.897E-12 3.482E-13 3.235E-11 1.937E-15 274.75 .51 1250 9.866E-11 5.508E-12 2.288E-13 2.743E-11 1.808E-15 268.45 .33 1450 1.999E-10 1.100E-11 5.622E-13 5.242E-11 *** 272.10 .39 TOTAL 7.777E-10 4.190E-11 2.911E-12 1.896E-10 1.709E-14 277.14 GAS

NO PLATEAU

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. 83 ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit

v 06/13/9? v 06/13/92 04:22:29 23 Jan 1993 91-543 #37,38,39 RD87

ro C_J)

.1

350 91-543 HORNBLENDE

OJ czn 300

OJ c_ ro o_ o_ 250

200 I I 39 84 0 An, RELEASED (%) 100

v 06/13/92 (40/36in = 295.5) v 06/13/92 04:48:27 23 Jan 1993 91-543 #37,38,39 RD87 Point deleted; 9 points regressed out of 9 Mean X = .529E-01 Mean Y = .377E-04 Slope = -.149E-01 a+g .340E-02 36/40 = .828E-03 a+g . 180E-03 39/40 = . 554E-01 a+g .757E-03 Fit parameters: SUMS = 14.316 MSWD = 2.045 40Ar/36Ar = 1207.56 a+g 262.58 F = 18.04 a+g .246 AGE = 271.58 a+g 3.67 Ma

91-543 OJ

IT) I

CO m

in i

I ,01 .02 .03 .04 .05 85 .06 39 Ar/40Ar v 06/13/92 92-111 #58 RD91 05:53:50 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34869 900 254974 14767 136 18 96 200 EALL 171 9 9 12 6 34870 950 458360 29757 381 0 25 200 BALL 207 15 15 12 6 34871 1000 218973 14049 119 0 16 200 EALL 46 9 9 4 7 34872 1075 165256 10440 83 14 24 200 EALL 89 10 19 17 5 34873 1150 330076 21417 330 8 20 200 EALL 230 46 23 6 6

CORRECT IONS

TEMP 39Ar 37Ar K-derived Ca-derived Cl-der Initial C Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

900 10 91 84 198 0 000 -0 18 950 19 0 169 399 0 000 -0 5 1000 9 0 80 189 0 000 -0 3 1075 7 74 59 140 0 000 -0 4 1150 14 40 122 287 0 000 0 4

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/Cl (Ma) sample package package

A 900 16.3 88.8 70.82 0 15. 304 244.68 - 1.71 2.06 2.36 B 950 32.9 98.4 0.00 0 15. 122 241.96 - .84 1.41 1.81 C 1000 15.5 97.8 0.00 0 15. 222 243.46 2.13 2.42 2.67 D 1075 11.5 95.7 61.46 0 15. 122 241.96 2.22 2. SO 2.74 E 1150 23.7 98.2 234.09 1120 15. 112 241.81 - 1.29 1.72 2.06 Total gas K/Ca = 74.1

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 -.5 J = 0.009492 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.67 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.1167 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE-t-00-2 . 2E-03 3839 = 1. 3E-02-2 . 4E-04 4039 = 5 . 7E-03-4 . OE-03 v 06/13/92 23 Jan 1993 92-111 #58 RD91

J := 0 .009492 0.50% SAMPLE WT - 0.0107 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

900 7. 958E-12 4 .617E-13 * * * 3 .390E-15 3.018E-15 244. 68 1.71 950 1. 431E-11 9 .304E-13 *** *** * ** 241. 96 .84 1000 6. 834E-12 4 .393E-13 ** * *** *** 243. 46 2.13 1075 5. 158E-12 3 .264E-13 ** * 2 .762E-15 * ** 241. 96 2.22 1150 1. 030E-11 6 .697E-13 1.447E-15 1 .488E-15 *** 241. 81 1.29 TOTAL 4. 456E-11 2 .828E-12 1.447E-15 7 .640E-15 5.676E-15 242.60 GAS

100.0% of gas on plateau, steps 900 through 1150 PLATEAU AGE = 242.38 + 1.27

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit v 06/13/92

87 v 06/13/92 05:54:29 23 Jan 1993 92-111 #58 RD91

1000 E

ru C_D 100

10

350

cu en 92-111 300 MUSCOVITE cu c_ OD OL 250

200 I I 88 0 39 ArK RELEASED (%} 100

v 06/13/92 (40/36in = 295.5) v 06/13/92 05:57:31 23 Jan 1993 92-111 #58 RD91

5 points regressed out of 5 Mean X = .619E-01 Mean Y = .198E-03 Slope = -.465E-01 a+g .436E-02 36/40 = .307E-02 a+g .271E-03 39/40 = .662E-01 a+g .505E-03 Fit parameters: SUMS = .214 MSWD = .071 40Ar/36Ar = 325.2 a+g 28.61 F = 15.11 a+g .115 AGE = 241.77 a+g 2.06 Ma

92-111

LO m

cu

CO m

cu CZ3

.01 .02 .03 .04 .05 .06 89 -07 39 Ar/ 40Ar v 06/13/92 92-109 #54 RD91 06:20:11 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34847 1650 1327376 82420 1766 70 40 BALL 116 28 6 12

CORRECTIONS

TEMP 39Ar 37Ar K-derived Ca-derived Cl-der Initial |c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1650 53 19 469 1106 13

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP AGE intra- intra- inter- C 39Ar YIELD K/Ca K/Cl (Ma) sample package package

A 1650 100.0 98.4 1882.27 296 15.824 247.99 .33 1.21 1.67 Total gas K/Ca =

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 ».5 J = 0.009312 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 2.26 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.67 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.1167 ESPLIT 1: 7.77 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.0E-03

J = 0.009312 0.50% SAMPLE WT = 0.0250 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* ** C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1650 9.363E-11 5.824E-12 4.768E-14 *** 4.948E-15 247.99 .33

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** l-$iQjma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit v 06/13/92~ / 04/05/92 90-153 H8L RD85 #116 MUL 8K COR = K 17:06:48 2 Jun 1992

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD regression CURRENT OPTION

31114 1040 492488 28117 2543 115890 137 200 EALL t 549 42 37 900 10 31115 1050 411679 24351 2158 100144 129 200 EALL t 364 7 17 60 10 31116 1060 398562 23849 2084 102166 110 200 EALL t 813 49 9 1229 8 31117 1080 2394779 142113 11933 560175 551 200 EALL t 2934 231 31 1047 10 31118 1100 1004716 59720 4774 226300 204 200 EALL t 365 39 18 90 10 31119 1125 352292 21067 1740 81463 95 200 EALL t 540 48 21 185 7 31120 1150 685415 40765 3522 159154 180 200 EALL t 1245 78 30 294 7 31121 1175 353571 21096 1746 81066 86 200 EALL t 837 42 19 65 7

C 0 R R E C T IONS

TFMPi trir 39Ar 37Ar ucri i vcxj ----Ca-derived---- Cl-der Initial °c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1040 10 204820 157 371 0 211 10 83 0 9 1050 8 177140 136 322 0 182 9 72 0 10 1060 8 180871 133 315 0 186 9 73 0 6 1080 49 992544 796 1877 0 1022 48 401 1 25 1100 21 401304 334 789 0 413 * 19 162 0 7 1125 7 144581 118 278 0 149 7 58 0 6 1150 14 282705 228 539 0 291 14 114 0 11 1175 7 144118 118 279 0 148 7 58 0 5

All values in counts, corrected for mass discrimination

91 04/05/92 90-153 HBL RD85 #116 MUL BK COR = < 17:06:50 2 Jun 1992

precision TEMP X TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/Cl (Ma) s ample package package

1040 7.8 97.0 .05 31 17 .239 253.18 * 1.38 1.82 2.17 1050 6.7 96.2 .05 32 16 .489 242.88 ± 1.71 2.06 2.36 1060 6.6 97.5 .04 33 16 .534 243.50 ± 1.38 1.79 2.13 1080 39.4 98.4 .05 34 16.809 247.28 * .40 1.23 1.69 1100 16.5 99.0 .05 37 16 .879 248.24 ± .65 1.33 1.77 1125 5.8 97.2 .05 35 16 .481 242.77 ± 1.46 1.85 2.18 1150 11.3 97.4 .05 33 16 .606 244.49 ± .83 1.42 1.82 1175 5.8 97.9 .05 35 16 .640 244.95 ± 1.51 1.90 2.22 otal gas K/Ca = 0.0 recisions are 1 sigma, measured in Ma. Measured 40/36 atm = 286.8 ±.5 = 0.008740 ± 0.50% (intra-package) ± 0.50% (inter-package) rap current factors- 40: 5.66 100: 2.62 200: 1 anifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2 ESPLIT 1: 6.6 ESPLIT 2: 21.78 ensitivity = 1.000E-17 X Reproducibility = .25 Detection limit = 40 counts ata reduced assuming initial 40/36 = 295.50 ± 0.00 a-factors: 3637=2.6E-04±1.7E-06 3837=3.2E-05±2.4E-07 3937=6.7E-04*3.7E-06 -factors: 3739*0.OE+00±2.2E-03 3839=1.3E-02±2.4E-04 4039=5.7E-03*4.0E-03

J = 0.008740 i: 0.50% SAMPLE UT = 0.1009 g

Initial & Potassium Chlorine Calcium EMP radiogenic derived derived derived Initial AGE* ** C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1 040 9.847E-12 5.542E-13 4.267E-14 6.273E-12 9.926E-16 253.18 ± 1.38 1050 8.231E-12 4.800E-13 3.613E-14 5.423E-12 1.072E-15 242.88 ± 1.71 1060 7.969E-12 4.699E-13 3.472E-14 5.536E-12 *** 243.50 t 1.38 1080 4.788E-11 2.802E-12 1.971E-13 3.037E-11 2.651E-15 247.28 ± .40 1100 2.009E-11 1.178E-12 7.803E-14 1.227E-11 *** 248.24 ± .65 1125 7.043E-12 4.154E-13 2.870E-14 4.421E-12 *** 242.77 ± 1.46 1150 1.370E-11 8.038E-13 5.859E-14 8.642E-12 1.206E-15 244.49 ± .83 1175 7.069E-12 4.160E-13 2.878E-14 4.404E-12 *** 244.95 ± 1.51 TOTAL 1.218E-10 7.119E-12 5.048E-13 7.734E-11 8.466E-15 246.64 GAS

55.9% of gas on plateau, steps 1080 through 1100 PLATEAU AGE = 247.55 + 1.29

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 ± 0 ** 1-sigma precision estimates are for intra-sample reproducibiIity. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibiIity. *** below detection limit

v 04/05/92 ' 04/05/92 17:07:48 2 Jun 1992 90-153 HBL RD85 #116 MUL BK COR = K

.1

(TD C_J)

.01

350

03 90-153 HORNBLENDE CD 300

05 C_ CO

250

200 I I I 0 100 39AnK RELEASED (%) 93

v 04/05/92 (40/36in = 295.5) ' 04/05/92 17:17:02 2 Jun 1992 90-153 H8L RD85 #116 MUL BK COR = < oint A deleted; 7 points regressed out of 8 includes 92.2 % of 39Ar ean X = .587E-01 Mean Y = .833E-04 Slope = -.565E-01 * .602E-01 6/40 = .340E-02 + .353E-02 39/40 = .601E-01 + .168E-02 it parameters: SUMS = 4.07 MSWO = .814 OAr/36Ar = 294.54 + 306.24 F = 16.63 + .465 AGE = 244.82 + 6.51 Ma

90-153 HORNBLENDE

OJ CD CD CD

in i

CD

CO m

(

.01 .02 .03 .04 .05 .06 94 39 Ar/"°Ar W/0 POINTS A v 06/13/92 92-110 #33 RD91 03:14:20 21 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34803 1100 2502029 137783 17662 209866 952 200 ESPLIT 763 69 29 285 6 34804 1135 1454169 82525 10572 140231 596 200 ESPLIT 459 27 40 221 5 34805 1250 4559506 245798 31747 423999 2469 200 EALL 7902 331 33 903 12 34806 1500 687387 18186 2434 31406 1377 200 EALL 230 16 8 52 8

COR R E C T IONS

TT?M D o iy f\L. .J / f\L. K-derived Ca-derived Cl-der Initial c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1100 88 1047903 779 1838 0 849 40 333 3 116 1135 52 700730 466 1100 0 567 27 223 2 70 1250 156 2120075 1388 3276 0 1717 81 673 5 336 1500 12 157134 103 242 0 127 6 50 0 249

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 1100 45.2 92.7 .06 21 16.903 264.80 .21 1.26 1.76 B 1135 27.1 92.4 .05 21 16.365 256.94 .27 1.23 1.72 C 1250 25.8 88.3 .05 21 16.472 258.51 .52 1.32 1.79 D 1500 1.9 42.8 .05 18 16.253 255.31 1.89 2.32 2.61 Total gas K/Ca = .1

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 -.5 J = 0.009354 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.1167 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839 = 1. 3E-02-2 . 4E-04 4039=5 . 7E-03 -4 . OE-03

95 v 06/13/92 03: 14:23 21 Jan 1993 92-110 #33 RD91 : ^i J = 0 .009354 0.50% SAMPLE WT = 0. 2499 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1100 2. 435E-10 1 .335E-11 1.551E-12 1.228E-10 6 .037E-14 264 .80 .21 1135 1. 415E-10 7 .991E-12 9.281E-13 8.208E-11 3 .639E-14 256 .94 .27 1250 1. 423E-10 7 .632E-12 8.986E-13 7.963E-11 5 .617E-14 258 .51 .52 1500 2. 146E-11 5 .647E-13 7.614E-14 5.901E-12 4 .156E-14 255 .31 1.89 TOTAL 5. 488E-10 2 .954E-11 3.454E-12 2.904E-10 1 .945E-13 260.87 GAS

54.8% of gas on plateau, steps 1135 through 1500 PLATEAU AGE = 257.28 + 1.34

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit v 06/13/92

96 v 06/13/92 03:14:59 21 Jan 1993 92-110 #33 RD91

.1

CO

.01

92-110 HORNBLENDE

ro

CD CD F 250 d CD c_ ro CZL CZL

200 I I 39 0 Ar\ RELEASED (%} 97 100

v 06/13/92 (40/36in = 295.5) v 06/13/92 03:24:03 21 Jan 1993 92-110 #33 RD91 Point A deleted; 3 points regressed out of 4 includes 54.8 % of 39Ar Mean X = .537E-01 Mean Y = 408E-03 Slope = -.557E-01 .474E-03 36/40 = .340E-02 a+£ .257E-04 39/40 = .610E-01 a+g .903E-04 Fit parameters: SUMS = 5.365 MSWD = 5.365 40Ar/36Ar = 294.24 a-HJ 2.22 F = 16.394 a+9 .024 AGE = 257.37 a+£ 1.25 Ma

92-110

_ m

.01 .02 .03 .04 .05 .06 98 W/0 POINTS A v 06/13/92 92-122 #35 RD91 03:05:42 1 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34775 1100 753697 24805 1146 84046 1354 200 EALL 365 38 10 118 12 34776 1125 942517 49553 1886 175212 845 200 EALL 469 35 11 47 7 34777 1200 1931464 109331 4083 385895 1363 200 EALL 419 29 11 619 7 34778 1350 643277 27025 1154 94240 884 200 EALL 224 20 11 141 6

C 0 R R E C T IONS

TTlufD 3 y AJL O / r\JL K-derived Ca- -derived Cl-der Initial C Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1100 16 412325 139 328 0 335 16 131 0 229 1125 31 860040 278 656 0 698 33 274 0 107 1200 69 1895190 613 1447 0 1539 72 604 0 143 1350 17 463073 152 358 0 376 18 148 0 138

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 1100 11.8 51.9 .03 57 15.952 253.74 2.17 2.51 2.78 B 1125 23.5 82.0 .02 91 15.794 251.40 .63 1.35 1.79 C 1200 51.9 88.3 .02 96 15.796 251.43 .31 1.23 1.71 D 1350 12.8 66.0 .02 70 15.913 253.18 1.04 1.60 2.00 Total gas K/Ca = 0.0 Precisions are 1 sigma, measured in Ma. Measured 40/36 atm - J = 0.009468 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.1167 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03

99 v 06/13/92 03:05:45 21 Jan 1993 92-122 #35 RD91

J = 0.009468 0.50% SAMPLE WT = 0.1012 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1100 2.353E-11 7. 651E-13 3.227E-14 1 .554E-11 3 .831E-14 253. 74 2.17 1125 2.942E-11 1. 528E-12 4.084E-14 3 .240E-11 1 .791E-14 251. 40 .63 1200 6.028E-11 3. 370E-12 8.474E-14 7 .140E-11 2 .384E-14 251. 43 .31 1350 2.008E-11 8. 333E-13 2.868E-14 1 .744E-11 2 .308E-14 253. 18 1.04 TOTAL 1.333E-10 6. 496E-12 1.865E-13 1 .368E-10 1 .031E-13 251.92 GAS

100.0% of gas on plateau, steps 1100 through 1350 PLATEAU AGE = 251.60 + 1.31

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit

v 06/13/92

100 v 06/13/92 03:06:20 21 Jan 1993 92-122 #35 RD91

.1 c

ro

.01

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CTD

OJ CD 250

OJ C_ CTD

200 I I 0 39 Ar\ RELEASED (%} 101 100

v 06/13/92 (40/36in = 295.5) v 06/13/92 03:09:53 21 Jan 1993 92-122 #35 RD91 Point deleted; 4 points regressed out of 4 Mean X = .449E-01 Mean Y = .975E-03 Slope = -.526E-01 a+g .933E-03 36/40 = .334E-02 a+g .429E-04 39/40 = .634E-01 a+g .370E-03 Fit parameters: SUMS = .103 MSWD = .051 40Ar/36Ar = 299.57 a+g 3.85 F = 15.762 a+g .092 AGE = 250.94 a+g 1.8 Ma

92-122

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,01 ,02 .03 .04 .05 .06 102 39 Ar/ 40Ar v 06/13/92 91-550 #6,7,8 RD87 03:22:14 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

32597 1075 225544 12294 978 19173 25 200 BALL 70 11 16 23 4 32598 1100 456751 25993 2242 41864 67 200 BALL 712 32 13 37 1 32599 1125 1317485 76199 6501 124968 139 200 BALL 928 59 14 178 9 32600 1150 2083850 121299 10345 199435 187 200 BALL 1281 83 15 338 6 32601 1175 3246397 189444 16093 312322 248 200 BALL 2961 427 32 310 9 32602 1200 1730753 101282 8491 164905 115 200 ESPLIT 578 39 5 326 8 32603 1250 1465293 85919 7135 138991 99 200 ESPLIT 755 79 18 133 5 32604 1450 2255485 131296 10976 216283 181 200 BALL 1440 139 13 220 7

CORK E C T IONS

TEMP 39Ar 37Ar K-derived Ca-derived Cl-der Initial |c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1075 3 17769 70 165 0 25 1 10 0 3 1100 6 38835 147 348 0 54 3 21 0 9 1125 17 116049 432 1020 0 163 8 64 0 14 1150 28 185396 688 1624 0 260 12 102 1 16 1175 43 290617 1075 2536 0 407 19 160 1 17 1200 23 153624 575 1356 0 215 10 84 0 6 1250 20 129634 488 1150 0 181 9 71 0 5 1450 30 201917 745 1757 0 282 13 111 1 13

All values in counts, corrected for mass discrimination

103 v 06/13/92 91-550 #6,7,8 RD87 03:22:16 23 Jan 1993

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 1075 1.0 98.0 .17 36 17 .995 271 .54 - 1.37 1.87 2.25 B 1100 2.2 97.0 .17 33 17 .064 258 .45 - .43 1.28 1.76 C 1125 6.5 98.3 .16 34 17 .010 257 .69 - .54 1.32 1.79 D 1150 10.3 98.8 .16 34 16 .984 257 .33 - .25 1.23 1.72 E 1175 16.1 99.2 .16 34 17 .011 257 .71 .30 1.24 1.73 F 1200 28.5 99.5 .16 34 17 .010 257 .69 - .36 1.26 1.74 G 1250 24.1 99.4 .17 35 16 .969 257 .12 - .29 1.24 1.72 H 1450 11.2 99.1 .16 34 17 .032 258 .00 .27 1.24 1.73 Total gas K/Ca = .2

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 -.5 J = 0.009027 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.51 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.344E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03

J = 0.009027 0.50% SAMPLE WT = 1.0085 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* ** C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1075 6.061E-12 3.301E-13 2.196E-14 9.955E-13 *** 271.54 - 1.37 1100 1.227E-11 6.980E-13 5.117E-14 2.175E-12 1.229E-15 258.45 .43 1125 3.540E-11 2.046E-12 1.478E-13 6.495E-12 2.027E-15 257.69 .54 1150 5.600E-11 3.257E-12 2.350E-13 1.037E-11 2.291E-15 257.33 - .25 1175 8.723E-11 5.087E-12 3.651E-13 1.625E-11 2.374E-15 257.71 .30 1200 1.535E-10 8.975E-12 6.338E-13 2.833E-11 *** 257.69 - .36 1250 1.299E-10 7.613E-12 5.316E-13 2.389E-11 *** 257.12 - .29 1450 6.061E-11 3.525E-12 2.483E-13 1.127E-11 1.904E-15 258.00 .27 TOTAL 5.410E-10 3.153E-11 2.235E-12 9.977E-11 1.547E-14 257.71 GAS

99.0% of gas on plateau, steps 1100 through 1450 PLATEAU AGE = 257.64 + 1.34

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package r epr oduc *£$£. ity. *** below detection limit

v 06/13/92 v 06/13/92 03:23:00 23 Jan 1993 91-550 #6,7,8 RD87

ro C_J>

91-550 HORNBLENDE

CD CD 250

CD C_ no

200 39 0 Ar\ RELEASED (%} 105 100

v 06/13/92 (40/36in = 295.5) X v 06/13/92 03:26:03 23 Jan 1993 91-550 #6,7,8 RD87 Point A deleted; 7 points regressed out of 8 includes 99 % of 39Ar Mean X = .580E-01 Mean Y = .446E-04 Slope = -.494E-01 a+g .137E-01 36/40 = .291E-02 a+g .795E-03 39/40 = .589E-01 a+g .296E-03 Fit parameters: SUMS = .177 MSWD = .035 40Ar/36Ar = 343.5 a+g 93.8 F = 16.976 a+g .085 AGE = 257.21 a+g 1.7 Ma

91-550

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A

CO m in i

.01 .02 .03 .04 .05 .06 106 39 ArAr W/0 POINTS A v 06/13/92 91-550 #12 RD87 06:36:26 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34850 450 2345683 138031 3394 367 45 40 EALL 519 125 13 18

CORRECTIONS

TEMP 39Ar 37Ar K-derived Ca-derived Cl-der Initial |c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

450 185 13644 786 1854

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 450 100.0 99.5 5.12 215 16.866 256.00 .24 1.22 1.71 Total gas K/Ca = 5.1

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 -.5 J = 0.009040 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 2.26 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.1167 ESPLIT 1: 7.77 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03

J = 0.009040 0.50% SAMPLE WT = 0.0510 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

450 1.655E-10 9.760E-12 1.096E-13 9.911E-13 2.858E-15 256.00 .24

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. 107 ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit

v 06/13/92 06/13/92 92-107 #21,22,23,24 RD91 01:00:25 21 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34670 1100 1269785 59748 2037 141807 694 200 EALL 888 57 13 156 5 34671 1125 2853958 158219 4580 338777 1010 200 EALL 2006 140 11 423 4 34672 1150 530058 25299 763 49688 403 200 EALL 143 16 15 34 5 34673 1175 248977 9521 306 21147 307 200 EALL 90 9 11 38 16 34674 1200 489174 23181 780 51592 370 200 EALL 212 15 6 73 6 34675 1250 1091810 56053 1809 123604 544 200 EALL 499 29 13 157 7

C O R R E C T IONS

T'T^'MT^ Tl O TV . "5 T H T/ lll-)^*'.ivr l~\/-) _. ., .... f* » -J jc\i. -i / m. V-rQ -derived Cl-der Initial |c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1100 36 625984 337 795 0 518 24 203 0 S2 1125 95 1496280 893 2107 0 1238 58 486 0 99 1150 15 219577 143 337 0 182 9 71 0 62 1175 6 93499 54 127 0 77 4 30 0 52 1200 14 228236 131 309 0 189 9 74 0 56 1250 34 547101 316 746 0 453 21 178 0 69

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 1100 18.0 88.5 .04 109 18 .945 288 .00 .43 1.41 1.94 3 1125 47.7 94.5 .04 151 17 .157 262 .70 .21 1.25 1.75 C 1150 7.6 81.4 .05 127 17 .152 262 .63 - .78 1.46 1.91 D 1175 2.9 67.0 .04 100 17 .630 269 .43 7.31 7.42 7.53 E 1200 7.0 82.1 .04 107 17 .426 266 .54 1.09 1.66 2.08 F 1250 16.9 90.0 .04 121 17 .647 269 .68 .52 1.37 1.86 Total gas K/Ca = 0.0

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 «.5 J = 0.009137 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.1167 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivi-q^Qg: 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03 v 06/13/92 01:00:29 21 Jan 1993 92-107 #21,22,23,24 RD91

J := 0.009137 0.50% SAMPLE WT = 1.0002 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE * * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1100 3.963E-11 1.852E-12 4. 100E-14 2 .403E-11 I .540E-14 288. 00 - .43 1125 8.908E-11 4.908E-12 7. 871E-14 5 .744E-11 I .647E-14 262. 70 - .21 1150 1.654E-11 7.854E-13 1. 502E-14 8 .428E-12 1 .041E-14 262. 63 - .78 1175 7.772E-12 2.953E-13 7. 121E-15 3 .588E-12 8 .684E-15 269. 43 7.31 1200 1.527E-11 7.189E-13 1. 62 IE-14 8 .759E-12 9 .275E-15 266. 54 - 1.09 1250 3.408E-11 1.738E-12 3. 477E-14 2 .099E-11 1 . 150E-14 269. 68 .52 TOTAL 2.024E-10 1.030E-11 1. 928E-13 1 .232E-10 7 .173E-14 268.91 GAS

58.2% of gas on plateau, steps 1125 through 1175 PLATEAU AGE = 262.70 + 1.37

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit v 06/13/92

109 06/13/92 05:17:31 23 Jan 1993 92-107 #21,22,23,24 RD91

. 1

l 1 HD LJ> -^ ^

.01

350

-« *»

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200 \l\\\\\\\ no 0 39 An K RELEASED (%) ^

v 06/13/92 (40/36in = 295.5) v 06/13/92 05:23:19 23 Jan 1993 92-107 #21,22,23,24 RD91

Point A deleted; 5 points regressed out of 6 includes 82 % of 39Ar Mean X = .533E-01 Mean Y = .290E-03 Slope = -.574E-01 a+£ .142E-02 36/40 = .335E-02 a+£ .761E-04 39/40 = .584E-01 a+£ .150E-03 Fit parameters: SUMS = 2.569 MSWD = .856 40Ar/36Ar = 298.22 a+£ 6.77 F = 17.126 a+£ .044 AGE = 262.26 a+£ 1.37 Ma

92-107

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.01 .02 .03 ,04 .05 111 .06 39 Ar/"°Ar W/0 POINTS A v 06/13/92 91-548 #103,104,105 RD85 00:58:17 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

30920 1050 1119429 61086 2144 196597 409 200 EALL 792 64 9 217 2 30921 1075 1617679 94597 4008 295767 304 200 ESPLIT 1613 154 6 230 5 30922 1100 1622928 95130 4795 290219 293 200 EALL 396 21 6 93 3 30923 1125 554490 32525 1633 98536 117 200 EALL 465 24 10 76 4 30924 1150 412064 23513 821 77989 133 200 EALL 190 13 10 67 8 30925 1175 291236 16587 568 54736 94 200 EALL 182 10 8 49 3 30926 1200 325499 18429 695 59155 99 200 EALL 25 9 6 47 10 30927 1250 413103 23815 878 76232 96 200 EALL 114 18 12 68 6

C 0 R R E C T IONS

TEMP 39Ar 37Ar K-derived ai-derived Cl-der Initial |c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1050 18 283648 346 815 0 324 15 127 0 53 1075 28 427186 535 1263 0 488 23 191 0 21 1100 28 419552 538 1270 0 479 23 188 0 20 1125 10 142577 184 434 0 163 8 64 0 10 1150 7 112948 133 314 0 129 6 51 0 16 1175 5 79346 94 221 0 90 4 35 0 11 1200 6 85829 104 246 0 98 5 38 0 11 1250 7 110706 135 318 0 126 6 49 0 9

All values in counts, corrected for mass discrimination

112 v 06/13/92 91-548 #103,104,105 RD85 00:58:18 23 Jan 1993

prec3.S3.on TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 1050 10.5 92.5 .07 107 17. 021 252. 79 .25 1.21 1.69 B 1075 53.5 97.9 .07 83 16. 807 249. 82 .31 1.21 1.68 C 1100 16.3 98.1 .07 65 16. 790 249. 57 .16 1.18 1.66 D 1125 5.6 97.2 .07 65 16. 625 247. 28 .57 1.29 1.73 E 1150 4.0 94.0 .06 109 16. 549 246. 22 1.42 1.83 2.16 F 1175 2.8 94.0 .06 113 16. 569 246. 50 .81 1.42 1.83 G 1200 3.2 94.5 .07 97 16. 753 249. 06 2.28 2.57 2.82 H 1250 4.1 96.7 .07 102 16. 835 250. 20 .96 1.52 1.92 Total gas K/Ca = .1

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 «.5 J = 0.008837 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 4.2 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.344E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02»2.4E-04 4039=5 . 7E-03-4. OE-03

J = 0.008837 0.50% SAMPLE WT = 0.9990 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1050 3.008E-11 1.635E-12 3.683E-14 1.294E-11 7.608E-15 252.79 .25 1075 1.434E-10 8.357E-12 2.440E-13 6.429E-11 1.008E-14 249.82 .31 1100 4.361E-11 2.547E-12 9.491E-14 1.913E-11 2.856E-15 249.57 .16 1125 1.490E-11 8.709E-13 3.237E-14 6.498E-12 1.425E-15 247.28 .57 1150 1.107E-11 6.293E-13 1.392E-14 5.145E-12 2.230E-15 246.22 1.42 1175 7.826E-12 4.440E-13 9.523E-15 3.613E-12 1.591E-15 246.50 .81 1200 8.747E-12 4.933E-13 1.229E-14 3.907E-12 1.632E-15 249.06 2.28 1250 1.110E-11 6.375E-13 1.518E-14 5.038E-12 1.247E-15 250.20 .96 TOTAL 2.708E-10 1.561E-11 4.590E-13 1.206E-10 2.867E-14 249.70 GAS

69.8% of gas on plateau, steps 1075 through 1100 PLATEAU AGE 249.64 + 1.30

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproduc ib ility. 113 *** below detection limit

v 06/13/92 v 06/13/92 00:58:53 23 Jan 1993 91-548 #103,104,105 RD85

. 1

OD 1_3 -^ ^1

.01

91-548

^ l" «S, HORNBLENDE ro s:

CD CD "* 250 i " . L_ vj W ^ > d CD C_ ro CZL CZL

200 1 1 1 1 1 1 1 1 114 '3 39 Ar K RELEASED (X) ^

v 06/13/92 (40/36in = 295.5) X v 06/13/92 01:06:45 23 Jan 1993 91-548 #103,104,105 RD85 Points DEFGH deleted; 3 points regressed out of includes 80.3 % of 39Ar Mean X = .560E-01 Mean Y = .179E-03 Slope = -.466E-01 a+£ .118E-02 36/40 = .278E-02 a+£ .660E-04 39/40 = .598E-01 a+£ .109E-03 Fit parameters: SUMS = .075 MSWD = .075 40Ar/36Ar = 359.24 a+£ 8.52 F = 16.725 a+< .03 AGE = 248.67 a+ 1.24 Ma

91-548

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.01 .02 .03 .04 .05 39 H/0 POINTS DEFGH v 06/13/92 H-548 #14 RD87 06:37:24 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34851 450 1120061 60394 1205 205 392 40 EALL 711 40 5 13 6

CORRECTIONS

TEMP 39Ar 37Ar K-derived Ca-derived Cl-der Initial IC Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

450 81 7635 344 811 73

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 450 100.0 89.7 4.00 312 16.590 252.47 - .47 1.28 1.74 Total gas K/Ca = 4.0

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 -.5 J = 0.009055 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 2.26 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.1167 ESPLIT 1: 7.77 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03

J = 0.009055 - 0.50% SAMPLE WT = 0.0500 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

450 7.901E-11 4.270E-12 3.307E-14 5.546E-13 2.763E-14 252.47 .47

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** l-sl^nfk precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit

v 06/13/92 v 06/13/92 92-103 #62 RD91 06:14:25 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34832 750 3998666 234424 3149 3617 591 200 ESPLIT 2906 161 3 12 10 34833 900 3172397 186233 2687 0 1158 200 EALL 2189 123 9 21 6 34834 950 1932216 122700 1675 35 230 200 ESPLIT 497 64 5 15 5 34835 1000 2311591 150069 2002 0 138 200 EALL 1099 83 8 9 4 34836 1050 1152371 73472 994 0 134 200 EALL 523 40 7 9 4 34837 1100 972983 61942 853 0 122 200 EALL 279 15 5 13 22 34838 1150 1719897 110552 1485 0 151 200 EALL 341 30 15 12 2 34839 1200 3113412 202646 2666 0 124 200 EALL 1575 98 17 16 12

C 0 R R E C T I 0 N S

TEMP 39Ar 37Ar \*ci UfcrlT XV GO, Cl-der Initial |c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

750 149 18009 1333 3146 0 15 1 6 0 110 900 118 0 1059 2499 0 000 0 217 950 78 174 698 1647 0 000 0 43 1000 95 0 854 2014 0 000 0 26 1050 47 0 418 986 0 000 0 25 1100 39 0 352 831 0 000 0 23 1150 70 0 629 1484 0 000 0 28 1200 129 0 1153 2719 0 000 -0 23

All values in counts, corrected for mass discrimination

117 v 06/13/92 92-103 #62 RD91 06:14:27 23 Jan 1993

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/Cl (Ma) sample package package

A 750 41.1 95.7 5.63 4839 16. 288 260. 33 .27 1.25 1.74 B 900 8.9 89.2 0.00 1101 15. 164 243. 52 .22 1.17 1.63 C 950 21.5 96.5 304.43 4012 15. 165 243. 54 .20 1.16 1.63 D 1000 7.2 98.2 0.00 20609 15. 103 242. 61 - .16 1.15 1.62 E 1050 3.5 96.5 0.00 5085 15. 114 242. 78 .25 1.17 1.63 F 1100 3.0 96.3 0.00 3293 15. 096 242. 51 1.57 1.94 2.25 G 1150 5.3 97.4 0.00 8282 15. 125 242. 94 .09 1.15 1.61 H 1200 9.7 98.8 0.00 0 15. 154 243. 38 .28 1.18 1.64 Total gas K/Ca = 67.7

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 -.5 J = 0.009531 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 2.26 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.67 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.1167 ESPLIT 1: 7.77 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.0E-03

J = 0.009531 0.50% SAMPLE WT = 0.1080 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

750 4.581E-10 2 .690E-11 1 .345E-14 2.485E-12 6. 733E-14 260. 33 .27 900 9.901E-11 5 .823E-12 1 .279E-14 * * * 3. 626E-14 243. 52 .22 950 2.214E-10 1 .408E-11 8 .495E-15 2.406E-14 2. 640E-14 243. 54 .20 1000 7.214E-11 4 .692E-12 * * * * ** 4. 318E-15 242. 61 .16 1050 3.597E-11 2 .297E-12 * * * * * * 4. 208E-15 242. 78 .25 1100 3.037E-11 1 .937E-12 1 .424E-15 * * * 3. 820E-15 242. 51 1.57 1150 5.368E-11 3 .457E-12 * * * *** 4. 721E-15 242. 94 .09 1200 9.717E-11 6 .336E-12 * * * *** 3. 882E-15 243. 38 .28 TOTAL 1.068E-09 6 .553E-11 3 .882E-14 2.509E-12 1. 509E-13 250.28 GAS

58.9% of gas on plateau, steps 900 through 1200 PLATEAU AGE = 243.04 + 1.27

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproduc iL)ii8. ity. *** below detection limit

v 06/13/92 v 06/13/92 06:15:05 23 Jan 1993 92-103 #62 RD91

1000

ru 100 10 1

350

ro 92-103 OJ MUSCOVITE CD 300

OJ c_ ru a. 250

200 0 39 ArK RELEASED (%) 119 100

v 06/13/92 (40/36in = 295.5) X v 06/13/92 05:51:12 23 Jan 1993 92-103 #62 RD91 Point A deleted; 7 points regressed out of 8 includes 58.9 % of 39Ar Mean X = .623E-01 Mean Y = .191E-03 Slope = -.498E-01 a+g .994E-03 36/40 = .329E-02 a+£ .620E-04 39/40 = .662E-01 a+g .927E-04 Fit parameters: SUMS = 2.907 MSWD = .581 40Ar/36Ar = 303.71 a+g 5.72 F = 15.116 a+g .021 AGE = 242.81 a+g 1.18 Ma

92-103

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RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34650 1025 659207 37185 2412 21593 131 200 EALL 696 29 7 26 19 34651 1050 1555483 91501 5915 52792 192 200 EALL 449 65 18 41 4 34652 1075 2290952 135830 8734 78266 236 200 EALL 1174 104 18 56 5 34653 1100 3495861 208292 13364 119894 313 200 EALL 1634 159 29 24 6 34654 1125 1714926 102669 6543 58810 126 200 ESPLIT 359 50 8 79 4 34655 1150 4607744 276203 17511 157070 306 200 EALL 2368 221 5 166 6 34656 1175 502331 29189 1860 16536 53 200 EALL 48 9 14 21 6 34657 1200 771416 45431 2862 25909 95 200 EALL 563 54 8 33 6 34658 1250 2732229 162741 10340 92732 208 200 EALL 1509 120 10 37 6

CORK E C T IONS

TEMP 39Ar 37Ar ed - Ca-derived Cl-der Initial C Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1025 22 94235 211 498 0 78 4 31 0 19 1050 54 230515 519 1225 0 191 9 75 1 22 1075 81 341933 771 1819 0 284 13 111 1 23 1100 124 524080 1182 2789 0 434 20 170 2 26 1125 61 257239 583 1375 0 213 10 84 1 8 1150 164 687407 1568 3699 0 570 27 224 2 15 1175 17 72406 166 391 0 60 3 24 0 5 1200 27 113513 258 608 0 94 4 37 0 11 1250 97 406492 924 2179 0 337 16 132 1 14

All values in counts, corrected for mass discrimination

121 v 06/13/92 92-102 #41,42,43,44 RD91 02:41:00 19 Jan 1993

precision TEMP % TOT RAD APP APP F AGE intra- intra- inter- C 39Ar YIELD K/Ca K/C1 (Ma) sample package package

A 1025 2.8 95.5 .17 47 16 .931 263 .78 2.18 2.51 2.79 B 1050 7.0 97.8 .17 47 16 .627 259 .36 .21 1.23 1.73 C 1075 10.3 98.4 .17 47 16 .600 258 .98 - .21 1.23 1.72 D 1100 15.9 98.8 .17 48 16 .588 258 .80 .17 1.22 1.72 E 1125 24.9 99.3 .17 48 16 .587 258 .79 .16 1.22 1.72 F 1150 21.0 99.5 .17 48 16 .600 258 .97 .16 1.22 1.72 G 1175 2.2 98.3 .17 48 16 .921 263 .63 .94 1.55 1.98 H 1200 3.5 97.8 .17 49 16 .606 259 .06 .56 1.34 1.80 I 1250 12.4 99.2 .17 48 16 .657 259 .80 .21 1.23 1.73 Total gas K/Ca = .2

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 «.5 J = 0.009300 0.50% (intra-package) « 0.50% (inter-package) Trap current factors- 40: 5.66 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.3 SPLIT 2: 10.89 SPLIT 3: 35.937 BALL: 2.07 ESPLIT 1: 6.6 ESPLIT 2: 21.78 Sensitivity = 1.470E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03

J = 0.009300 0.50% SAMPLE WT = 1.0016 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* * * C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

1025 2.005E-11 1.131E-12 5.884E-14 3.533E-12 3.070E-15 263.78 2.18 1050 4.732E-11 2.782E-12 1.434E-13 8.643E-12 3.561E-15 259.36 .21 1075 6.969E-11 4.130E-12 2.112E-13 1.282E-11 3.796E-15 258.98 .21 1100 1.063E-10 6.334E-12 3.227E-13 1.965E-11 4.308E-15 258.80 « .17 1125 1.663E-10 9.955E-12 5.023E-13 3.074E-11 4.082E-15 258.79 .16 1150 1.402E-10 8.399E-12 4.209E-13 2.576E-11 2.483E-15 258.97 .16 1175 1.528E-11 8.876E-13 4.487E-14 2.713E-12 ** * 263.63 - .94 1200 2.347E-11 1.382E-12 6.893E-14 4.253E-12 1.772E-15 259.06 .56 1250 8.311E-11 4.949E-12 2.488E-13 1.523E-11 2.290E-15 259.80 .21 TOTAL 6.717E-10 3.995E-11 2.022E-12 1.233E-10 2.624E-14 259.27 GAS

79.1% of gas on plateau, steps 1050 through 1150 PLATEAU AGE = 258.95 + 1.35

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** l-sigb&2precision estimates are for intra-sample reproducibility. ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproducibility. *** below detection limit

v 06/13/92 v 06/13/92 02:41:45 19 Jan 1993 92-102 #41,42,43,44 RD91

ru CJ)

92-102 HORNBLENDE ro D

OJ CD 250

OJ c_ CO

200 39 0 An, RELEASED (%} 123 100

v 06/13/92 (40/36in = 295.5) X v 06/13/92 02:47:29 19 Jan 1993 92-102 #41,42,43,44 RD91

Points AGHI deleted; 5 points regressed out of 9 includes 79.1 % of 39Ar Mean X = .595E-01 Mean Y = .427E-04 Slope = -.505E-01 .316E-01 36/40 = .305E-02 a+$ .188E-02 39/40 = .603E-01 a-t-g .588E-03 Fit parameters: SUMS = .017 MSWD = .006 40Ar/36Ar = 328.37 a+£ 202.37 F = 16.577 a+ .162 AGE = 258.64 2.64 Ma

92-102

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.01 .02 .03 .04 ,05 .06 124 39 ArAr W/0 POINTS AGHI v 06/13/92 92-104 #56 RD91 06:21:16 23 Jan 1993

RAW DATA

FILE TEMP 40Ar 39Ar 38Ar 37Ar 36Ar TRAP MANIFOLD a regression CURRENT OPTION

34848 450 921039 59853 3834 46 40 EALL 417 16 24

CORRECTIONS

TEMP 39Ar 37Ar K-derived Ca-derived Cl-der Initial |c Decay Decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

450 38 340 803

All values in counts, corrected for mass discrimination

precision TEMP % TOT RAD APP APP AGE intra- intra- inter- C 39Ar YIELD K/Ca K/Cl (Ma) sample package package

A 450 100.0 98.5 0.00 48 15.135 242.42 .53 1.25 1.69 Total gas K/Ca = 0.0

Precisions are 1 sigma, measured in Ma. Measured 40/36 atm = 296.5 «.5 J = 0.009503 0.50% (intra-package) 0.50% (inter-package) Trap current factors- 40: 2.26 100: 2.26 200: 1 Manifold factors- ALL: 1 SPLIT 1: 3.67 SPLIT 2: 10.89 SPLIT 3: 35.937 EALL: 2.1167 ESPLIT 1: 7.77 ESPLIT 2: 21.78 Sensitivity = 1.475E-17 % Reproducibility = .25 Detection limit = 40 counts Data reduced assuming initial 40/36 = 295.50 0.00 Ca-factors: 3637=2.6E-04-1.7E-06 3837=3.2E-05-2.4E-07 3937=6.7E-04-3.7E-06 K-factors: 3739=0.OE+00-2.2E-03 3839=1.3E-02-2.4E-04 4039=5.7E-03-4.OE-03

J = 0.009503 0.50% SAMPLE WT = 0.0255 g

Initial & Potassium Chlorine Calcium TEMP radiogenic derived derived derived Initial AGE* ** C 40Ar 39Ar 38Ar 37Ar 36Ar in Ma

450 6.496E-11 4.229E-12 2.149E-13 *** 3.221E-15 242.42 .53

Note: all gas quantities are in moles. No blank correction. * Ages calculated assuming initial 40Ar/36Ar = 295.5 0 ** 1-sigma precision estimates are for intra-sample reproducibility. 125 ** 1-sigma precision estimates for plateaux are for intra-irradiation package reproduc ibility. *** below detection limit

v 06/13/92 ACKNOWLEDGEMENT

This work has been partially supported by NSF Grants EAR 91- 04495, 88-03540, the Connecticut Geological and Natural History Survey, and a grant in aid in research from the Geological Society of America. We thank H. Cortesini, Jr. for his comments on the manuscript, Bonnie Jackson for help in typing, and the McHones of Moodus, Connecticut, and Sid Quarrier for field support.

REFERENCES

Aitken, J. M., 1955, The bedrock geology of the Rockville quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 6, 55p., map.

Alexander, E.G., Jr., Mickelson, G.M., and Lanphere, M.A., 1978, Mmhb-1: a new 40Ar/39Ar dating standard, in Zartman, R.E., ed., Short papers of the fourth international conference, geochronology, cosmochronology, isotope geology 1978: U.S. Geological Survey Open-File Report 78-701, p.6-8.

Ambers, Clifford P., 1988, Metasomatism associated with ductile deformation in a granodioritic gneiss, central Connecticut:Master's thesis at Indiana University, Bloomington, 86p.

Boyd, J.L., Wintsch, R.P., and Kunk, MJ., 1993, Possible Polymetamorphism in the Bronson Hill Terrane: A 100 M.Y. Age Gradient in 40Ar/39Ar Hornblende Ages: Geological Soc. America - Northeastern Section, Abstracts with Programs, v.25, p.A6.

Brookins, Douglas G., 1970, A summary of geochronological data for pegmatites of the Middletown, Connecticut, area accumulated mainly since 1952: Conn. Geol. Nat. History Survey Rept. No. 5, p.10-18.

Brookins, D.G., and Armstrong, R.L., 1980, New K-Ar dates for pegmatites and host rocks, Portland, Connecticut: Contributions to geochronology in Connecticut, II. Report-of-Investigations- Connecticut, State Geol. and Nat. History Survey Rept. No. 10, p.37- 40.

Collins, G. E., 1954, The bedrock geology of the Ellington quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 4, 44p., map.

126 Dalrymple, G.B., Alexander, E.G., Lanphere,M.A., and Kraker, G.P., 1981, Irradiation of samples for 40Ar/39Ar dating using the Geological Survey TRIGA reactor: U.S. Geol. Survey Prof. Paper 1176, 55p.

Dodson, M.H., 1973, Closure temperature in cooling geochronological and petrological systems: Gontrib. Mineral. Petrol., v. 40, 259-274.

Fahey, RJ., and Pease, M.H., 1977, Bedrock geologic map of the South Coventry quadrangle, Tolland County, Connecticut: U.S. Geological Survey Open File Report, 28p.

Fleck, RJ., Sutter, J.F., and Elliot, D.H., 1977, Interpretation of discordant 40Ar/39Ar age spectra of Mesozoic tholeiites from Antarctica: Geochim. Cosmochim. Acta, v.41, p. 15-32.

Harrison, T. M., and Spear, F.S., Heizler, M.T., 1989, Geochronological studies in central New England II: Post-Acadian hinged and differential uplift: Geology, v.17, p.185-189.

Haugerud, R.A., and Kunk, MJ., 1988, ArAr*, a computer program for reduction of 40Ar-39Ar data: U.S. Geol. Survey, Open File Rept. 88- 261, 68p.

Herz, Norman, 1955, The bedrock geology of the Glastonbury quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 5, 22p., map.

Lundgren, Lawrence, Jr., 1963, The bedrock geology of the Deep River quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 13, 4Op., map.

Lundgren, Lawrence, Jr., 1964, The bedrock geology of the Essex quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 15, 37p., map.

Lundgren, Lawrence, Jr., 1979, The bedrock geology of the Haddam quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 37, 44p., map.

Lundgren, Lawrence, Jr., and Thurrell, R. F., 1973, The bedrock geology of the Clinton quadrangle: Conn. Geol. Nat. History Survey Quad. Rept. 29, 22p., map.

127 Michener, Stuart R., 1983, Bedrock geology of the Pelham-Shutesbury syncline, Pelham Dome, West-Central Massachusetts: M.S. thesis at University of Massachusetts, Amherst, Contribution No.43, lOlp.

Peper, J. D., 1977a, Bedrock geology of the Hampden quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-1368.

Peper, J. D., 1977B, Bedrock geology of the Monson quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-1374.

Pressel, D.C., and Armstrong, R.L., 1980, K/Ar dates for granitic rocks and the Honey Hill Fault southeastern Connecticut: Contributions to geochronology in Connecticut, II. Report-of-Investigations- Connecticut, State Geol. and Nat. History Survey No. 10, p. 1-4.

Robinson, P., Tracy, RJ., Hollocher, K.T., Schumacher, J.C., Berry, H.N.IV., 1986, The Central Massachusetts Metamorphic High: in Robinson, Peter (ed.), Field Trip Guidebook: Regional Metamorphism and Metamorphic Phase Relations in Northwestern and Central New England, Contribution No. 59, Department of Geology and Geography University of Massachusetts, Amherst, Massachusetts, 288p.

Rodgers, John, 1985, Compiler, Bedrock geologic map of Connecticut, scale 1:125,000, State Geologic and Natural History Survey of Connecticut, Hartford.

Snee, L. W., Sutter, J. F., and Kelly, W. C., 1988, Thermochronology of economic mineral deposits: Dating the states of mineralization at Panasqueira, Portugal, by high-precision 40Ar/39Ar age spectrum techniques on muscovite: Economic Geology, v.83, p.335-354.

Snyder, G. L., 1970, Bedrock geology of the Marlborough quadrangle: U.S. Geol. Survey Geol. Quad. Map GQ-791.

Spear, F.S., and Harrison, T. M., 1989, Geochronological studies in central New England I: Evidence for pre-Acadian metamorphism in eastern Vermont: Geology, v.17, p.181-184.

Steiger, R.H., and Jager, E., 1977, Subcommission on geochronology: Convention on the use of decay constants in geo-and cosmo- chronology: Earth and Planetary Science Letters, v.36, p.359-363.

128 Tucker, R. D., and Robinson, Peter, 1990, Age and setting of the Bronson Hill magmatic arc: A re-evaluation based on U-Pb zircon ages in southern New England: Geological Society of America bulletin, v.102, p.1404-1419.

Tucker, R.D., and Robinson, P., 1993, U-Pb dating of the "Acadian" and "Alleghanian" metamorphic zones of central Massachusetts: Geological Society of America-National Meeting, Abstracts with Programs, v. 25, no. 6, p. A486.

Wintsch, R. P., Kunk, M. J., Cortesini, H. Jr., and Sutter, J. F., 1991: 40Ar/39Ar Age-spectrum data for the Avalon and Putnam-Nashoba litho tec tonic zones, eastern Connecticut and western Rhode Island: U.S. Geological Survey Open File Report 91-399, p.91-399.

Wintsch, R. P., and Sutter, J. F., 1986: A tectonic model for the late Paleozoic of southern New England: Journal of Geology, v.94, p.459- 472.

Wintsch, R.P., Sutter, J.F., Kunk, MJ., Aleinikoff, and Boyd,J.L., 1993a, Alleghanian assembly of Proterozoic and Paleozoic lithotectonic terranes in south central New England: New constraints from geochronology and petrology, In Gheney, J.T. and Hepburn, J.G. eds. Field trip guidebook for the northeastern United States: 1993 Boston GSA, V. 1, p. H1-H30.

Wintsch, R.P., Sutter, J.F., Kunk, M J., Aleinikoff, J.N., BoydJ.L. and Hellickson, B.P., 1993b, Geochronologic evidence for an Alleghanian assembly age of Proterozoic and Paleozoic lithotectonic terranes in south-Central New England,Geological Society of America, Abstacts with Programs,v. 25, p. A-478.

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